LAB Labranche & Co., Inc.

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a)
of the Securities Exchange Act of 1934

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MERGER PROPOSED—YOUR VOTE IS VERY IMPORTANT

         LaBranche & Co Inc. (which we refer to as LaBranche) and Cowen Group, Inc. (which we refer to as Cowen) have entered into an Agreement and Plan of Merger, dated as of February 16, 2011 (which we refer to as the merger agreement). Pursuant to the terms of the merger agreement, a wholly owned subsidiary of Cowen will merge with and into LaBranche (which we refer to as the merger). Immediately thereafter, Cowen will cause LaBranche to be merged with and into Louisiana Merger Sub, LLC, a wholly owned subsidiary of Cowen (which we refer to as Merger Sub LLC).

         Upon completion of the merger, LaBranche stockholders will receive 0.9980 shares of Cowen Class A common stock for each share of LaBranche common stock that they own (which we refer to as the exchange ratio). This exchange ratio is fixed and will not be adjusted to reflect stock price changes prior to the closing of the merger. Based on the closing price of Cowen Class A common stock on the NASDAQ Global Select Market on February 16, 2011, the last trading day before public announcement of the merger, the exchange ratio represented approximately $4.71 in value for each share of LaBranche common stock. Based on the closing price of Cowen Class A common stock on May 3, 2011, the latest practicable trading day before the date of this joint proxy statement/prospectus, the exchange ratio represented approximately $4.00 in value for each share of LaBranche common stock. Cowen stockholders will continue to own their existing Cowen shares. LaBranche common stock is currently traded on the New York Stock Exchange under the symbol "LAB," and Cowen Class A common stock is currently traded on the NASDAQ Global Select Market under the symbol "COWN." We urge you to obtain current market quotations of LaBranche common stock and Cowen Class A common stock.

         We intend for the merger and the related transactions, taken together, to qualify as a reorganization for U.S. federal income tax purposes. Accordingly, LaBranche stockholders are not expected to recognize any gain or loss for U.S. federal income tax purposes upon the exchange of shares of LaBranche common stock for shares of Cowen Class A common stock pursuant to the merger, except with respect to cash received in lieu of fractional shares of Cowen Class A common stock.

         Based on the estimated number of shares of LaBranche and Cowen common stock that will be outstanding immediately prior to the closing of the merger, we estimate that, upon closing, existing Cowen stockholders will own approximately 64.5% of Cowen and former LaBranche stockholders will own approximately 35.5% of Cowen.

         LaBranche and Cowen will each hold special meetings of their respective stockholders in connection with the proposed merger. At the special meeting of Cowen stockholders, Cowen stockholders will be asked to vote on the proposal to approve the issuance of shares of Cowen Class A common stock to LaBranche stockholders pursuant to the merger. The proposal to issue shares of Cowen Class A common stock will be approved if the holders of a majority of the outstanding shares of Cowen capital stock present in person or represented by proxy at the Cowen special meeting and entitled to vote on the proposal vote to approve the share issuance. At the special meeting of LaBranche stockholders, LaBranche stockholders will be asked to vote on the proposal to approve and adopt the merger agreement and approve the merger. The proposal to approve and adopt the merger agreement and approve the merger will be approved if the holders of a majority of the outstanding shares of LaBranche common stock entitled to vote on the proposal vote to approve and adopt the merger agreement and approve the merger.

         We cannot complete the merger unless the stockholders of each company approve the proposals made by each company as described above. Your vote is very important, regardless of the number of shares you own. Whether or not you expect to attend either special meeting in person, please submit a proxy to vote your shares as promptly as possible so that your shares may be represented and voted at the LaBranche or Cowen special meeting, as applicable.

          The LaBranche board of directors has unanimously approved the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of LaBranche and its stockholders. The LaBranche board of directors unanimously recommends that the LaBranche stockholders vote "FOR" the proposal to approve and adopt the merger agreement and approve the merger.

          The Cowen board of directors has unanimously approved the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the issuance of shares of Cowen Class A common stock to LaBranche stockholders pursuant to the merger, are in the best interests of Cowen and its stockholders. The Cowen board of directors unanimously recommends that the Cowen stockholders vote "FOR" the proposal to approve the issuance of shares of Cowen Class A common stock to LaBranche stockholders pursuant to the merger.

          The obligations of LaBranche and Cowen to complete the merger are subject to the satisfaction or waiver of several conditions. The accompanying joint proxy statement/prospectus contains detailed information about LaBranche, Cowen, the special meetings, the merger agreement and the merger. You should read this joint proxy statement/prospectus carefully and in its entirety before voting, including the section entitled "Risk Factors" beginning on page 37.

         We look forward to the successful completion of the merger.

         Sincerely,

George M.L. LaBranche, IV Chairman, Chief Executive Officer and President LaBranche & Co Inc.		Peter A. Cohen Chairman and Chief Executive Officer Cowen Group, Inc.

          Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of the securities to be issued under this joint proxy statement/prospectus or determined if this joint proxy statement/prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

         This joint proxy statement/prospectus is dated May 4, 2011 and is first being mailed to LaBranche and Cowen stockholders on or about May 6, 2011.

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NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

To the Stockholders of LaBranche & Co Inc.:

        You are cordially invited to attend the special meeting of stockholders of LaBranche & Co Inc. (which we refer to as LaBranche), which will be held at the Down Town Association, 60 Pine Street, New York, New York 10005 on June 15, 2011, at 9:00 a.m., local time, for the following purposes:

•

to consider and vote on the proposal to approve and adopt the Agreement and Plan of Merger, dated as of February 16, 2011 by and among Cowen Group, Inc., a Delaware corporation (which we refer to as Cowen), LaBranche and Louisiana Merger Sub, Inc., a Delaware corporation and a direct wholly-owned subsidiary of Cowen (which we refer to as the merger agreement), a copy of which is included as Annex A to the joint proxy statement/prospectus accompanying this notice, and approve the merger contemplated thereby; and



•

to vote upon the proposal to adjourn the LaBranche special meeting, if necessary or appropriate, to solicit additional proxies if there are not sufficient votes to approve the foregoing proposal.

        LaBranche will transact no other business at the special meeting except such business as may properly be brought before the special meeting or any adjournment or postponement thereof. Please refer to the joint proxy statement/prospectus of which this notice forms a part for further information with respect to the business to be transacted at the LaBranche special meeting.

         The LaBranche board of directors has unanimously approved the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of LaBranche and its stockholders. The LaBranche board of directors unanimously recommends that LaBranche stockholders vote "FOR" the proposal to approve and adopt the merger agreement and approve the merger and "FOR" the proposal to adjourn the LaBranche special meeting if necessary to solicit additional proxies in favor of such adoption.

        The LaBranche board of directors has fixed the close of business on May 4, 2011 as the record date for determination of LaBranche stockholders entitled to receive notice of, and to vote at, the LaBranche special meeting or any adjournments or postponements thereof. Only holders of record of LaBranche common stock at the close of business on the record date are entitled to receive notice of, and to vote at, the LaBranche special meeting. Approval and adoption of the merger agreement and approval of the merger requires the affirmative vote of holders of a majority of the outstanding shares of LaBranche common stock. A list of the names of LaBranche stockholders of record will be available for inspection for any purpose germane to the special meeting during ordinary business hours at LaBranche's headquarters located at LaBranche & Co Inc., 33 Whitehall Street, New York, NY 10004, for ten days prior to the LaBranche special meeting. The LaBranche stockholder list will also be available at the LaBranche special meeting for examination by any stockholder present at such meeting.

        All stockholders are invited to attend the special meeting in person. However, whether or not you plan to attend the special meeting in person, you are urged to vote by any of the three methods below:

        (1)   By internet: go to www.proxyvote.com —have your proxy card available when you access the web site and follow the instructions to obtain your records and vote;

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        (2)   By phone: call toll-free number for telephone voting can be found on the enclosed proxy card; or

        (3)   By mail: complete and return the enclosed proxy card in the postage prepaid envelope provided.

        If your shares are held in the name of a broker, bank or other stockholder of record, please follow the voting instructions that you receive from the stockholder of record entitled to vote your shares. Stockholders who attend the special meeting may revoke their proxy and vote their shares in person.

        The enclosed joint proxy statement/prospectus provides a detailed description of the merger and the merger agreement. We urge you to read this joint proxy statement/prospectus, including any documents incorporated by reference, and the Annexes carefully and in their entirety. If you have any questions concerning the merger or this joint proxy statement/prospectus, would like additional copies or need help voting your shares of LaBranche common stock, please contact LaBranche's proxy solicitor:

Morrow & Co., LLC
470 West Avenue
Stamford, Connecticut 06902
(888) 681-0976 (toll free)
(203) 658-9400
Labranche.info@morrowco.com

New York, New York
May 4, 2011

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NOTICE OF SPECIAL MEETING OF STOCKHOLDERS

To the Stockholders of Cowen Group, Inc.:

        We are pleased to invite you to attend the special meeting of stockholders of Cowen Group, Inc. (which we refer to as Cowen) which will be held at The InterContinental The Barclay, Park Avenue Room, 111 East 48th Street, New York, New York 10017 on June 15, 2011, at 3:00 p.m., local time, to consider and vote on the following:

•

a proposal to approve the issuance of shares of Cowen Class A common stock to LaBranche & Co Inc. (which we refer to as LaBranche) stockholders (which we refer to as the Cowen stock issuance) pursuant to the merger (which we refer to as the merger) as contemplated by the Agreement and Plan of Merger, dated as of February 16, 2011, by and among LaBranche, Cowen and Louisiana Merger Sub, Inc., a wholly owned subsidiary of Cowen (which we refer to as the merger agreement), a copy of which is included as Annex A to the joint proxy statement/prospectus of which this notice forms a part; and



•

a proposal to adjourn the Cowen special meeting, if necessary, to solicit additional proxies if there are not sufficient votes at the time of the special meeting to approve the foregoing proposal.

        Cowen will transact no other business at the special meeting except such business as may properly be brought before the special meeting or any adjournment or postponement thereof. Please refer to the joint proxy statement/prospectus of which this notice forms a part for further information with respect to the business to be transacted at the special meeting.

        Completion of the merger is conditioned on, among other things, approval of the Cowen stock issuance.

         The Cowen board of directors has unanimously approved the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the Cowen stock issuance, are in the best interests of Cowen and its stockholders. The Cowen board of directors unanimously recommends that Cowen stockholders vote "FOR" the proposal to approve the Cowen stock issuance and "FOR" the proposal to adjourn the Cowen special meeting, if necessary, to solicit additional proxies.

        The Cowen board of directors has fixed the close of business on May 4, 2011 as the record date for determination of Cowen stockholders entitled to receive notice of, and to vote at, the Cowen special meeting or any adjournments or postponements thereof. Only Cowen stockholders of record at the close of business on the record date are entitled to receive notice of, and to vote at, the Cowen special meeting. The Cowen stock issuance requires the affirmative vote of holders of a majority of the outstanding shares of Cowen Class A common stock present in person or represented by proxy at the Cowen special meeting and entitled to vote on the proposal. A list of the names of Cowen stockholders of record will be available for ten days prior to the Cowen special meeting for any purpose germane to the special meeting between the hours of 9:00 a.m. and 5:00 p.m., local time, at Cowen's headquarters, 599 Lexington Avenue, New York, NY 10022. The Cowen stockholder list will also be available at the Cowen special meeting for examination by any stockholder present at such meeting.

         Your vote is very important. For your convenience, in addition to submitting a proxy to vote your shares by signing and returning the enclosed proxy card in the postage-paid envelope provided, we have also made telephone and internet voting available to you. Simply follow the instructions on the enclosed proxy card. If your shares are held in a 401(k) plan or in the name of a bank, broker or

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other fiduciary, please follow the instructions on the voting instruction card furnished by the plan trustee or administrator, or record holder, as appropriate.

        The enclosed joint proxy statement/prospectus provides a detailed description of the merger and the merger agreement as well as a description of the Cowen stock. We urge you to read this joint proxy statement/prospectus, including any documents incorporated by reference, and the Annexes carefully and in their entirety. If you have any questions concerning the merger or this joint proxy statement/prospectus, would like additional copies or need help voting your shares of Cowen Class A common stock, please contact Cowen's proxy solicitor:

MacKenzie Partners, Inc.
105 Madison Avenue
New York, NY 10016
Call Collect: (212) 929-5500
or
Toll Free: (800) 322-2885

		By Order of the Board of Directors of Cowen Group, Inc.,
		Owen S. Littman General Counsel and Secretary

New York, New York
May 4, 2011

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REFERENCES TO ADDITIONAL INFORMATION

        This joint proxy statement/prospectus incorporates important business and financial information about LaBranche and Cowen from documents that are not included in or delivered with this joint proxy statement/prospectus. This information is available to you without charge upon your request. You can obtain the documents incorporated by reference into this joint proxy statement/prospectus free of charge by requesting them in writing or by telephone from the appropriate company at the following addresses and telephone numbers:

         If you would like to request any documents, please do so by June 6, 2011 in order to receive them before the special meetings.

        For a more detailed description of the information incorporated by reference in this joint proxy statement/prospectus and how you may obtain it, see "Where You Can Find More Information" beginning on page 143.

ABOUT THIS JOINT PROXY STATEMENT/PROSPECTUS

        This joint proxy statement/prospectus, which forms part of a registration statement on Form S-4 filed with the U.S. Securities and Exchange Commission (which we refer to as the SEC) by Cowen, constitutes a prospectus of Cowen under the Securities Act of 1933, as amended (which we refer to as the Securities Act), with respect to the shares of Cowen Class A common stock to be issued to LaBranche stockholders pursuant to the merger. This joint proxy statement/prospectus also constitutes a joint proxy statement for both LaBranche and Cowen under the Securities Exchange Act of 1934, as amended (which we refer to as the Exchange Act). It also constitutes a notice of meeting with respect to the special meeting of Cowen stockholders and a notice of meeting with respect to the special meeting of LaBranche stockholders.

        You should rely only on the information contained in or incorporated by reference into this joint proxy statement/prospectus. No one has been authorized to provide you with information that is different from that contained in, or incorporated by reference into, this joint proxy statement/prospectus. This joint proxy statement/prospectus is dated May 4, 2011, and you should assume that the information contained in this joint proxy statement/prospectus is accurate only as of such date. You should assume that the information incorporated by reference into this joint proxy statement/prospectus is only accurate as of the date of such information. Neither the mailing of this joint proxy statement/prospectus to LaBranche stockholders or Cowen stockholders nor the issuance by Cowen of shares of Class A common stock pursuant to the merger will create any implication to the contrary.

         This joint proxy statement/prospectus does not constitute an offer to sell, or a solicitation of an offer to buy, any securities, or the solicitation of a proxy in any jurisdiction to or from any person to whom it is unlawful to make any such offer or solicitation in such jurisdiction. Information contained in this joint proxy statement/prospectus regarding LaBranche has been provided by LaBranche and information contained in this joint proxy statement/prospectus regarding Cowen has been provided by Cowen.

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        All references in this joint proxy statement/prospectus to "LaBranche" refer to LaBranche & Co Inc., a Delaware corporation; all references in this joint proxy statement/prospectus to "Cowen" refer to Cowen Group, Inc., a Delaware corporation; all references to "Merger Sub" refer to Louisiana Merger Sub, Inc., a Delaware corporation and wholly owned subsidiary of Cowen formed for the purpose of effecting the merger; all references to "Merger Sub LLC" refer to Louisiana Merger Sub, LLC, a Delaware limited liability company and wholly owned subsidiary of Cowen formed for the purpose of effecting the transactions contemplated by the merger agreement, and, unless otherwise indicated or as the context requires, all references to the "merger agreement" refer to the Agreement and Plan of Merger, dated as of February 16, 2011, by and among LaBranche, Cowen and Merger Sub, a copy of which is included as Annex A to this joint proxy statement/prospectus.

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QUESTIONS AND ANSWERS

         The following are some questions that you, as a stockholder of Cowen or a stockholder of LaBranche, may have regarding the merger, the Cowen stock issuance and the other matters being considered at the special meetings and the answers to those questions. LaBranche and Cowen urge you to carefully read the remainder of this joint proxy statement/prospectus because the information in this section does not provide all the information that might be important to you with respect to the merger, the Cowen stock issuance and the other matters being considered at the special meetings. Additional important information is also contained in the Annexes to and the documents incorporated by reference into this joint proxy statement/prospectus.

Q:    Why am I receiving this joint proxy statement/prospectus?

A:

You are receiving this document because you were a stockholder of record of LaBranche or Cowen on the record date for the LaBranche special meeting or the Cowen special meeting, respectively. LaBranche and Cowen have agreed to a merger pursuant to the terms of the merger agreement that is described in this joint proxy statement/prospectus. A copy of the merger agreement is included in this joint proxy statement/prospectus as Annex A.

In order to complete the merger, among other things:

•

LaBranche stockholders must approve and adopt the merger agreement and approve the merger; and



•

Cowen stockholders must approve the issuance of shares of Cowen Class A common stock to LaBranche stockholders pursuant to the merger;

LaBranche and Cowen will hold separate special meetings of their respective stockholders to obtain these approvals. This joint proxy statement/prospectus, including its Annexes, contains and incorporates by reference important information about Cowen and LaBranche, the merger, the Cowen stock issuance and the stockholder meetings of Cowen and LaBranche. You should read all the available information carefully and in its entirety. The enclosed proxy card and instructions allow you to vote your shares without attending the special meeting in person.

Your vote is important. You are encouraged to vote as soon as possible.

Q:    What will I receive in the merger?

A:

LaBranche Stockholders : If the merger is completed, holders of LaBranche common stock will receive 0.9980 shares of Cowen Class A common stock for each share of LaBranche common stock they hold at the effective time of the merger. LaBranche stockholders will not receive any fractional shares of Cowen Class A common stock in the merger. Instead, Cowen will pay cash in lieu of any fractional shares of Cowen Class A common stock that a LaBranche stockholder would otherwise have been entitled to receive.

Cowen Stockholders : If the merger is completed, Cowen stockholders will not receive any merger consideration and will continue to hold their shares of Cowen Class A common stock.

Q:    What is the value of the merger consideration?

A:

Because Cowen will issue 0.9980 shares of Cowen Class A common stock in exchange for each share of LaBranche common stock, the value of the merger consideration that LaBranche stockholders receive will depend on the price per share of Cowen Class A common stock at the effective time of the merger. That price will not be known at the time of the special meetings and may be less than the current price or the price at the time of the special meetings. Based on the closing price of Cowen Class A common stock on the NASDAQ Global Select Market on

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February 16, 2011, the last trading day before public announcement of the merger, the exchange ratio represented approximately $4.71 in value for each share of LaBranche common stock, which had a closing price of $4.06 per share on February 16, 2011. Based on the closing price of Cowen Class A common stock on May 3, 2011, the latest practicable trading day before the date of this joint proxy statement/prospectus, the exchange ratio represented approximately $4.00 in value for each share of LaBranche common stock, which had a closing price of $3.92 per share on May 3, 2011, the latest practicable trading day before the date of this joint proxy statement/prospectus. Cowen stockholders will continue to own their existing Cowen shares. Cowen Class A common stock is currently traded on the NASDAQ Global Select Market under the symbol "COWN," and LaBranche common stock is currently traded on the New York Stock Exchange under the symbol "LAB." We urge you to obtain current market quotations of Cowen Class A common stock and LaBranche common stock.

Q:    Can I attend the special meeting and vote my shares in person?

A:

Yes. If you are a LaBranche or Cowen stockholder of record, you may vote your shares in person at the applicable meeting by completing a ballot at the meeting. Even if you currently plan to attend the meeting, it is recommended that you also submit your proxy as described above, so your vote will be counted if you later decide not to attend the meeting. If you submit your vote by proxy and later decide to vote in person at the meeting, the vote you submit at the meeting will override your proxy vote. If you are a street name holder, you may vote your shares in person at the meeting only if you obtain and bring to the meeting a signed letter or other form of proxy from your broker, bank, trust company or other nominee giving you the right to vote the shares at the meeting.

Q:    How can I attend the meeting?

A:

LaBranche Stockholders : All of LaBranche's stockholders are invited to attend the LaBranche special meeting. You may be asked to present valid photo identification, such as a driver's license or passport, before being admitted to the meeting. If you hold your shares in street name, you also may be asked to present proof of ownership to be admitted to the meeting. A brokerage statement or letter from your broker, bank, trust company or other nominee proving ownership of the shares on May 4, 2011, the record date for the LaBranche special meeting, are examples of proof of ownership.

To help LaBranche plan for the meeting, please indicate whether you expect to attend by responding affirmatively when prompted during internet or telephone voting or by marking the attendance box on the proxy card.

Cowen Stockholders : All of Cowen's stockholders are invited to attend the Cowen special meeting. You may be asked to present valid photo identification, such as a driver's license or passport, before being admitted to the meeting. If you hold your shares in street name, you also may be asked to present proof of ownership to be admitted to the meeting. A brokerage statement or letter from your broker, bank, trust company or other nominee proving ownership of the shares on May 4, 2011, the record date for the Cowen special meeting, are examples of proof of ownership.

To help Cowen plan for the meeting, please indicate whether you expect to attend by responding affirmatively when prompted during internet or telephone voting or by marking the attendance box on the proxy card.

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Q:    When and where will the special stockholders meetings be held?

A:

LaBranche Stockholders : The special meeting of LaBranche stockholders will be held at the Down Town Association, 60 Pine Street, New York, New York 10005 on June 15, 2011, at 9:00 a.m., local time.

Cowen Stockholders : The special meeting of Cowen stockholders will be held at The InterContinental The Barclay, Park Avenue Room, 111 East 48th Street, New York, New York 10017 on June 15, 2011, at 3:00 p.m., local time.

Q:    Who is entitled to vote at the special stockholders meetings?

A:

LaBranche Stockholders : The board of directors of LaBranche has set May 4, 2011 as the record date for the LaBranche special meeting. If you were a stockholder of record of outstanding shares of LaBranche common stock at the close of business on May 4, 2011, you are entitled to vote at the meeting. As of the record date, 40,931,997 shares of LaBranche's common stock were outstanding.

Cowen Stockholders : The board of directors of Cowen has set May 4, 2011 as the record date for the Cowen special meeting. If you were a stockholder of record of outstanding shares of Cowen Class A common stock at the close of business on May 4, 2011, you are entitled to vote at the meeting. As of the record date, 75,665,037 shares of Cowen's Class A common stock, representing all of Cowen's voting stock, were issued and outstanding and, therefore, eligible to vote at the meeting.

Q:    What constitutes a quorum at the special stockholders meetings?

A:

LaBranche Stockholders : Stockholders who hold shares representing at least a majority of the issued and outstanding stock entitled to vote at the LaBranche special meeting must be present in person or represented by proxy to constitute a quorum for the transaction of business at the LaBranche special meeting.

Cowen Stockholders : Stockholders who hold shares representing at least a majority of the issued and outstanding shares entitled to vote at the Cowen special meeting must be present in person or represented by proxy to constitute a quorum for the transaction of business at the Cowen special meeting.

Q:    What does it mean if I receive more than one set of proxy materials?

A:

If you receive more than one set of proxy materials or multiple control numbers for use in submitting your proxy, it means that you hold shares registered in more than one account. To ensure that all of your shares are voted, sign and return each proxy card or voting instruction card you receive or, if you submit your proxy by internet or telephone, vote once for each card or control number you receive.

Q:    How do I vote if I am a stockholder of record?

A:

LaBranche Stockholders . If you are a stockholder of record of LaBranche as of the close of business on the record date for the LaBranche special meeting, you may vote in person by attending the LaBranche special meeting or, to ensure your shares are represented at the LaBranche special meeting, you may authorize a proxy to vote by:

•

accessing the internet site listed on the proxy card;

•

calling the toll-free number listed on the proxy card; or

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•

signing and returning the enclosed proxy card by mail.

If you hold LaBranche shares in street name you can vote your shares in the manner prescribed by your broker, bank, trust company or other nominee. Your broker, bank, trust company or other nominee has enclosed or otherwise provided a voting instruction card for you to use in directing such broker, bank, trust company or other nominee how to vote your shares. Without instructions from you, your broker, bank, trust company or other nominee cannot vote your shares, which will have the effect described below.

Cowen Stockholders . If you are a stockholder of record of Cowen as of the close of business on the record date for the Cowen special meeting, you may vote in person by attending the Cowen special meeting or, to ensure your shares are represented at the Cowen special meeting, you may authorize a proxy to vote by:

•

accessing the internet site listed on the proxy card;



•

calling the toll-free number listed on the proxy card; or



•

signing and returning the enclosed proxy card by mail.

If you hold Cowen shares in street name, you can vote your shares in the manner prescribed by your broker, bank, trust company or other nominee. Your broker, bank, trust company or other nominee has enclosed or otherwise provided a voting instruction card for you to use in directing such broker, bank, trust company or other nominee how to vote your shares. Without instructions from you, your broker, bank, trust company or other nominee cannot vote your shares, which will have the effect described below.

Q:    What are my voting rights?

A:

LaBranche Stockholders : Holders of LaBranche common stock are entitled to one vote per share. As of the close of business on the record date for the LaBranche special meeting, a total of 40,931,997 votes are entitled to be cast at the LaBranche special meeting.

Cowen Stockholders : Holders of Cowen's Class A common stock are entitled to one vote per share. As of the close of business on the record date for the Cowen special meeting, a total of 75,665,037 votes are entitled to be cast at the Cowen special meeting.

Q:    What vote is required to approve each proposal?

A:

LaBranche Stockholders : Approval and adoption of the merger agreement and approval of the merger requires the affirmative vote of holders of a majority of the outstanding shares of LaBranche common stock. Approval of the proposal to adjourn the LaBranche special meeting, if necessary, to solicit additional proxies requires the affirmative vote of holders of a majority of the outstanding shares of LaBranche common stock present in person or represented by proxy at the LaBranche special meeting and entitled to vote, even if less than a quorum. Each of George M.L. LaBranche, IV (Chairman, Chief Executive Officer and President of LaBranche), Alfred O. Hayward, Jr. (Executive Vice President of LaBranche) and William J. Burke, III (Chief Operating Officer of LaBranche) has entered into an agreement with Cowen to vote all shares of LaBranche common stock owned by that individual at the time of the LaBranche special meeting in favor of approval and adoption of the merger agreement and approval of the merger. In addition, Messrs. LaBranche and Hayward have agreed to direct the parties to that certain Stockholders' Agreement, effective August 18, 1999 (which we refer to as the LaBranche stockholders' agreement), by and among LaBranche and certain LaBranche stockholders, to vote all of their shares in favor of approval and adoption of the merger agreement and approval of the merger. Collectively, at the close of business for the record date for the LaBranche special meeting,

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Messrs. LaBranche, Burke and Hayward and the other LaBranche stockholders party to the LaBranche stockholders' agreement held approximately 14.7% of the outstanding shares of LaBranche common stock.

Cowen Stockholders : The Cowen stock issuance requires the affirmative vote of holders of a majority of the outstanding shares of Cowen Class A common stock present in person or represented by proxy at the Cowen special meeting and entitled to vote on the proposal. Approval of the proposal to adjourn the Cowen special meeting, if necessary, to solicit additional proxies requires the affirmative vote of holders of a majority of the outstanding shares of Cowen Class A common stock present in person or represented by proxy at the Cowen special meeting, even if less than a quorum. RCG Holdings LLC (which we refer to as RCG) has entered into an agreement with LaBranche to vote all shares of Cowen Class A common stock owned by RCG at the time of the Cowen special meeting in favor of the Cowen stock issuance. At the close of business for the record date of the Cowen special meeting, RCG held approximately 43.1% of the issued and outstanding Cowen Class A common stock.

Q:    How does the LaBranche board of directors recommend that LaBranche stockholders vote?

A:

The LaBranche board of directors has unanimously determined that the merger agreement and the transactions contemplated by the merger agreement, including the merger, are advisable and in the best interests of LaBranche and its stockholders. The LaBranche board of directors unanimously recommends that LaBranche stockholders vote "FOR" the proposal to approve and adopt the merger agreement and approve the merger and "FOR" the proposal to adjourn the LaBranche special meeting, if necessary, to solicit additional proxies.

Q:    How does Cowen's board of directors recommend that Cowen stockholders vote?

A:

The Cowen board of directors has unanimously determined that the merger agreement and the transactions contemplated by the merger agreement, including the Cowen stock issuance, are in the best interests of Cowen and its stockholders. Cowen's board of directors unanimously recommends that Cowen stockholders vote "FOR" the proposal to approve the Cowen stock issuance and "FOR" the proposal to adjourn the Cowen special meeting, if necessary, to solicit additional proxies.

Q:    What is the difference between a stockholder of record and a "street name" holder?

A:

If your shares are registered directly in your name, you are considered the stockholder of record with respect to those shares. If your shares are held in a stock brokerage account or by a bank, trust company or other nominee, then the broker, bank, trust company or other nominee is considered to be the stockholder of record with respect to those shares, while you are considered the beneficial owner of those shares. In the latter case, your shares are said to be held in "street name."

Q:    My shares are held in "street name" by my broker, bank or other nominee. Will my broker, bank
        or other nominee automatically vote my shares for me?

A:

No. Your broker cannot vote your shares on "non-routine" matters, as described below in the section titled "What will happen if I return my proxy card without indicating how to vote," without instructions from you. You should instruct your broker as to how to vote your shares, following the directions your broker provides to you. Please check the voting form used by your broker. If you do not provide your broker with instructions and your broker submits an unvoted proxy, your shares will be counted for purposes of determining a quorum but they will not be voted on any proposal on which your broker, bank or other nominee does not have discretionary authority. This

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is often called a "broker non-vote." Please note that you may not vote shares held in street name by returning a proxy card directly to LaBranche or Cowen or by voting in person at your special meeting unless you first obtain a proxy from your broker, bank or other nominee.

Q:    What will happen if I fail to vote or I abstain from voting?

A:

LaBranche Stockholders : If you do not vote, it will be more difficult for LaBranche to obtain the necessary quorum to approve and adopt the merger agreement and approve the merger.

You may vote "FOR," "AGAINST" or "ABSTAIN" on each of the proposals. An abstention and a broker non-vote will be counted for purposes of determining a quorum. However, if you are the stockholder of record, and you fail to vote by proxy or by ballot at the special meeting, your shares will not be counted for purposes of determining a quorum. Abstentions, failures to submit a proxy card or vote in person and broker non-votes will be treated in the following manner with respect to determining the votes received for each of the proposals:

•

an abstention, failure to submit a proxy card or vote in person or a broker non-vote will be treated as a vote "AGAINST" the proposal to approve and adopt the merger agreement and approve the merger;



•

an abstention will be treated as a vote "AGAINST" the proposal to approve any adjournment of the LaBranche special meeting; and



•

a failure to submit a proxy card or vote in person or a broker non-vote will have no effect on the proposal to approve any adjournment of the LaBranche special meeting.

Cowen Stockholders : If you do not vote, it will be more difficult for Cowen to obtain the necessary quorum to approve the Cowen stock issuance.

You may vote "FOR," "AGAINST" or "ABSTAIN" on each of the proposals. An abstention and a broker non-vote will be counted for purposed of determining a quorum. However, if you are the stockholder of record, and you fail to vote by proxy or by ballot at the special meeting, your shares will not be counted for purposes of determining a quorum. Abstentions, failures to submit a proxy card or vote in person and broker non-votes will be treated in the following manner with respect to determining the votes received for each of the proposals:

•

an abstention will be treated as a vote "AGAINST" the proposal to approve the Cowen stock issuance and the proposal to approve any adjournment of the Cowen special meeting;



•

a failure to submit a proxy card or vote in person or a broker non-vote will have no effect on the proposal to approve the Cowen stock issuance; and



•

a failure to submit a proxy card or vote in person or a broker non-vote will have no effect on the proposal to approve any adjournment of the Cowen special meeting.

Q:    What will happen if I return my proxy card without indicating how to vote?

A: LaBranche Stockholders : If you are a stockholder of record and you submit your proxy by internet, telephone or mail but do not specify how you want to vote your shares on a particular proposal, LaBranche will vote your shares:

•

FOR the proposal to approve and adopt the merger agreement and approve the merger; and



•

FOR the proposal to approve any adjournment of the LaBranche special meeting, if necessary, to solicit additional proxies.

If you are a street name holder and fail to instruct the broker, bank, trust company or other nominee that is the stockholder of record how you want to vote your shares on a particular

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proposal, those shares are considered to be "uninstructed." Stockholders of record have the discretion to vote uninstructed shares on specified routine matters, and do not have the authority to vote uninstructed shares on non-routine matters, such as the proposal to approve and adopt the merger agreement and approve the merger and the proposal to adjourn the LaBranche special meeting.

Cowen Stockholders : If you are a stockholder of record and you submit your proxy by internet, telephone or mail but do not specify how you want to vote your shares on a particular proposal, Cowen will vote your shares:

•

FOR the proposal to approve the Cowen stock issuance; and



•

FOR the proposal to approve any adjournment of the Cowen special meeting, if necessary, to solicit additional proxies.

If you are a street name holder and fail to instruct the broker, bank, trust company or other nominee that is the stockholder of record how you want to vote your shares on a particular proposal, those shares are considered to be "uninstructed." Stockholders of record have the discretion to vote uninstructed shares on specified routine matters, and do not have the authority to vote uninstructed shares on non-routine matters, such as the proposal to approve the Cowen stock issuance and the proposal to adjourn the Cowen special meeting.

Q:    Can I change my vote or revoke my proxy after I have returned a proxy or voting instruction card?

A:

Yes. If you are the holder of record of either LaBranche or Cowen common stock, you can change your vote or revoke your proxy at any time before your proxy is voted at your special meeting. You can do this in one of four ways:

•

by submitting a later-dated proxy by internet or telephone before the deadline stated on the enclosed proxy card;

•

by submitting a later-dated proxy card;

•

by sending a written notice of revocation to the Corporate Secretary of LaBranche or Cowen, as applicable, which must be received before the time of such special meeting; or

•

by voting in person at the special meeting.

If you are a street name holder, please refer to the voting instructions provided to you by your broker, bank, trust company or other nominee.

Any LaBranche common stockholder or Cowen common stockholder entitled to vote in person at the LaBranche or Cowen special meeting, respectively, may vote in person regardless of whether a proxy has been previously given, but simply attending such special meeting will not constitute revocation of a previously given proxy.

Q:    Who pays for the cost of proxy preparation and solicitation?

A:

In accordance with the terms of the merger agreement, LaBranche will bear the entire cost of proxy solicitation for the LaBranche special meeting, Cowen will bear the entire cost of proxy solicitation for the Cowen special meeting, and LaBranche and Cowen will share equally all expenses incurred in connection with the filing of the registration statement of which this document forms a part with the SEC and the printing and mailing of this document.

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Q:    Will LaBranche be required to submit the merger agreement to its stockholders even if LaBranche's board of
        directors has withdrawn (or amended or modified in a manner adverse to Cowen) its recommendation?

A:

Yes, unless LaBranche terminates the merger agreement and, concurrently, it enters into a definitive agreement with respect to a superior proposal (after complying with its obligations with respect to non-solicitation) and pays Cowen a termination fee of $6,250,000. For more information regarding the ability of LaBranche to terminate the merger in accordance with these conditions, see the sections entitled "The Merger Agreement—Termination of the Merger Agreement" beginning on page 106 and "The Merger Agreement—Termination Fees and Expenses; Liability for Breach," beginning on page 108.

Q:    Will Cowen be required to submit the Cowen stock issuance to its stockholders even if Cowen's board of
        directors has withdrawn (or amended or modified in a manner adverse to LaBranche) its recommendation?

A:

Yes. Cowen is required to submit the Cowen stock issuance to its stockholders even if Cowen's board of directors has withdrawn (or amended or modified in a manner adverse to LaBranche) its recommendation, consistent with the terms of the merger agreement.

Q:    What are the material U.S. federal income tax consequences of the merger to U.S. holders of LaBranche common
         stock?

A:

The merger and the related transactions, taken together, are intended to be treated for U.S. federal income tax purposes as a "reorganization" within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended (which we refer to as the Code). Assuming the merger and the related transactions, taken together, qualify as a reorganization, a holder of LaBranche common stock generally will not recognize any gain or loss for U.S. federal income tax purposes upon the exchange of the holder's shares of LaBranche common stock for shares of Cowen Class A common stock pursuant to the merger, except with respect to cash received in lieu of fractional shares. You should read the section titled "Material U.S. Federal Income Tax Consequences" beginning on page 112 for a more complete discussion of the U.S. federal income tax consequences of the merger and the related transactions. Tax matters can be complicated, and the tax consequences of the merger and the related transactions to you will depend on your particular tax situation. You should consult your tax advisor to determine the tax consequences of the transactions to you.

Q:    When do you expect the merger to be completed?

A:

LaBranche and Cowen hope to complete the merger as soon as reasonably practicable and currently expect the closing of the merger to occur by the end of the second quarter or the beginning of the third quarter of 2011. However, the merger is subject to various regulatory clearances and the satisfaction or waiver of other conditions, as described in the merger agreement, and it is possible that factors outside the control of LaBranche and Cowen could result in the merger being completed at an earlier time, a later time or not at all. There can be no assurances as to when or if the merger will close.

Q:    Do I need to do anything with my shares of common stock other than voting for the proposals at the special
        meeting?

A:

LaBranche Stockholders : If you are a LaBranche stockholder, after the merger is completed, each share of LaBranche common stock you hold will be converted into the right to receive 0.9980 shares of Cowen Class A common stock together with cash in lieu of any fractional shares, as

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applicable. You will receive instructions at that time regarding exchanging your shares for shares of Cowen Class A common stock. You do not need to take any action at this time. Please do not send your LaBranche stock certificates with your proxy card.

Cowen Stockholders : If you are a Cowen stockholder, after the merger is completed, you are not required to take any action with respect to your shares of Cowen Class A common stock.

Q:    Are stockholders entitled to appraisal rights?

A:

No. Neither the stockholders of Cowen nor the stockholders of LaBranche are entitled to appraisal rights in connection with the merger under Delaware law.

Q:    What happens if I sell my shares of LaBranche common stock before the LaBranche special meeting?

A:

The record date for the LaBranche special meeting is earlier than the date of the LaBranche special meeting and the date that the merger is expected to be completed. If you transfer your LaBranche shares after the LaBranche record date but before the LaBranche special meeting, you will retain your right to vote at the LaBranche special meeting, but will have transferred the right to receive the merger consideration in the merger. In order to receive the merger consideration, you must hold your shares through the effective date of the merger.

Q:    What if I hold shares in both LaBranche and Cowen?

A:

If you are a stockholder of both LaBranche and Cowen, you will receive two separate packages of proxy materials. A vote cast as a Cowen stockholder will not count as a vote cast as a LaBranche stockholder, and a vote cast as a LaBranche stockholder will not count as a vote cast as a Cowen stockholder. Therefore, please separately submit a proxy for each of your LaBranche and Cowen shares.

Q:    Who can help answer my questions?

A:

Cowen stockholders or LaBranche stockholders who have questions about the merger, the other matters to be voted on at the special meetings, or how to submit a proxy or desire additional copies of this joint proxy statement/prospectus or additional proxy cards should contact:

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SUMMARY

         This summary highlights information contained elsewhere in this joint proxy statement/prospectus and may not contain all the information that is important to you with respect to the merger, the Cowen stock issuance (which, together with the merger, we refer to as the transactions) and the other matters being considered at the LaBranche and Cowen special stockholder meetings. LaBranche and Cowen urge you to read the remainder of this joint proxy statement/prospectus carefully, including the attached Annexes, and the other documents to which we have referred you. See also the section entitled "Where You Can Find More Information" beginning on page 143. We have included page references in this summary to direct you to a more complete description of the topics presented below where appropriate.

The Companies

LaBranche & Co Inc.

        LaBranche & Co Inc., a Delaware corporation, is the parent corporation of LaBranche Structured Holdings, Inc., the holding company for a group of entities that are market-makers in options and exchange-traded funds, or "ETFs," traded on various exchanges, both domestically and internationally. Historically, and for part of the first quarter of 2011, LaBranche's business principally operated in two separate segments: the market-making segment and the institutional brokerage segment. The entities within LaBranche's market-making segment are market-makers on the NYSE Amex Exchange, the NYSE Arca Exchange, the NYBOT and other exchanges domestically and are market-makers on the London Stock Exchange and Euronext and Eurex exchanges, as well as on other exchanges and markets internationally. Prior to the sale of LaBranche's New York Stock Exchange designated market maker business on January 22, 2010, LaBranche was also one of the largest specialists/designated market makers on the New York Stock Exchange. As of December 31, 2010, LaBranche's market-making segment was comprised of market makers for 265 ETFs and 295 options. LaBranche's institutional brokerage segment began the process of winding down its business activities in the first quarter of 2011. Previously, the institutional brokerage segment provided securities execution services to institutional clients and professional traders.

        LaBranche's common stock is listed on the New York Stock Exchange under the symbol "LAB."

        The principal executive offices of LaBranche are located at 33 Whitehall Street, New York, NY 10004 and its telephone number is (212) 425-1144.

Cowen Group, Inc.

        Cowen Group, Inc., a Delaware corporation, is a diversified financial services firm and, together with its consolidated subsidiaries, provides alternative investment management, investment banking, research, and sales and trading services through its two business segments: alternative investment management and broker-dealer. The alternative investment management segment includes hedge funds, replication products, mutual funds, managed futures funds, fund of funds, real estate, healthcare royalty funds, and cash management services offered primarily under the Ramius name. The broker-dealer segment offers industry focused investment banking for growth-oriented companies including advisory and global credit markets origination and domain knowledge-driven research and a sales and trading platform for institutional investors, primarily under the "Cowen" name.

        Cowen's Class A common stock is traded on the NASDAQ Global Select Market under the symbol "COWN."

        The principal executive offices of Cowen are located at 599 Lexington Avenue, New York, NY 10022 and its telephone number is (212) 845-7900.

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Louisiana Merger Sub, Inc.

        Louisiana Merger Sub, Inc., a wholly owned subsidiary of Cowen Group, Inc., is a Delaware corporation that was formed on February 11, 2011 for the sole purpose of effecting the merger. In the merger, Louisiana Merger Sub, Inc. will be merged with and into LaBranche, with LaBranche continuing as the surviving corporation.

Louisiana Merger Sub, LLC

        Louisiana Merger Sub, LLC, a wholly owned subsidiary of Cowen Group, Inc., is a Delaware limited liability company that was formed on February 14, 2011. Immediately following the merger, LaBranche will be merged with and into Louisiana Merger Sub, LLC (which we refer to as the second-step merger), with Louisiana Merger Sub, LLC continuing as the surviving company.

Risk Factors

        In addition to other information included and incorporated by reference into this document, you should carefully read and consider the risks related to completion of the transactions, to Cowen following the transactions and the risks associated with each of the businesses of LaBranche and Cowen, beginning on page 37, before deciding whether to vote for the proposals presented in this document. Some of the most important risks are summarized below.

Risks Related to the Merger

•

The exchange ratio is fixed and will not be adjusted in the event of any change in either Cowen's or LaBranche's stock price.



•

The transactions are subject to conditions, including certain conditions that may not be satisfied, and may not be completed on a timely basis, or at all. Failure to complete the transactions could have a material and adverse effect on LaBranche.



•

The opinions obtained by Cowen's board of directors and LaBranche's board of directors from their respective financial advisors will not reflect changes in circumstances between the signing of the merger agreement and the completion of the transactions.



•

Some of LaBranche's respective current directors and executive officers have interests in the transactions that may differ from the interests of other LaBranche stockholders, as applicable, and these persons may have conflicts of interest in supporting or recommending that you approve the proposals set forth in this document.

Risks Related to Cowen Following the Transactions

•

Although LaBranche and Cowen expect that Cowen's acquisition of LaBranche will result in benefits to Cowen, Cowen may not realize those benefits because of integration difficulties and other challenges.



•

Current Cowen stockholders and LaBranche stockholders will have a reduced ownership and voting interest after the transactions and will exercise less influence over management.



•

The market price of Cowen's Class A common stock after the transactions will be affected by factors different from those currently affecting the market price of LaBranche's common stock.



•

The internal earnings estimates for LaBranche and the unaudited pro forma financial data for Cowen included in this joint proxy statement/prospectus are preliminary, and Cowen's actual financial position and operations after the transactions may differ materially from the unaudited pro forma financial data included in this joint proxy statement/prospectus.

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The Merger

        A copy of the merger agreement is attached as Annex A to this joint proxy statement/prospectus. LaBranche and Cowen encourage you to read the entire merger agreement carefully because it is the principal document governing the merger and the Cowen stock issuance. For more information on the merger agreement, see the section entitled "The Merger Agreement" beginning on page 93.

Effects of the Merger (see page 55)

        Subject to the terms and conditions of the merger agreement, at the effective time of the merger, Merger Sub, a newly formed subsidiary of Cowen, will be merged with LaBranche, with LaBranche continuing as the surviving corporation. Immediately thereafter, Cowen will merge LaBranche with Merger Sub LLC, a wholly owned subsidiary of Cowen, with Merger Sub LLC continuing as the surviving company and a wholly owned subsidiary of Cowen.

Terms of the Merger; Merger Consideration (see page 93)

        LaBranche stockholders will have the right to receive 0.9980 shares of Cowen Class A common stock for each share of LaBranche common stock they hold at the effective time of the merger (which we refer to as the exchange ratio). The exchange ratio is fixed and will not be adjusted for changes in the market value of the LaBranche common stock or Cowen Class A common stock. As a result, the implied value of the consideration to LaBranche stockholders will fluctuate between the date of this joint proxy statement/prospectus and the effective date of the merger. Based on the closing price of Cowen Class A common stock on the NASDAQ Global Select Market on February 16, 2011, the last trading day before public announcement of the merger, the exchange ratio represented approximately $4.71 in value for each share of LaBranche common stock. Based on the closing price of Cowen Class A common stock on the NASDAQ Global Select Market on May 3, 2011, the latest practicable trading day before the date of this joint proxy statement/prospectus, the exchange ratio represented approximately $4.00 in value for each share of LaBranche common stock, which had a closing price of $3.92 per share on May 3, 2011, the latest practicable trading day before the date of this joint proxy statement/prospectus.

Material U.S. Federal Income Tax Consequences (see page 112)

        As a condition to the completion of the merger, each of Willkie Farr & Gallagher LLP, tax counsel to Cowen, and Weil, Gotshal & Manges LLP, tax counsel to LaBranche, will deliver an opinion, dated as of the closing date of the merger, that the merger and the second-step merger, taken together, will be treated for U.S. federal income tax purposes as a "reorganization" within the meaning of Section 368(a) of the Code and that each of LaBranche and Cowen will be a party to the reorganization within the meaning of Section 368(b) of the Code. Neither Cowen nor LaBranche intends to waive this condition.

        The opinions regarding the merger and the second-step merger will not address any state, local or foreign tax consequences of the merger and the second-step merger. The opinions will be based on certain assumptions and representations as to factual matters from LaBranche and Cowen, as well as certain covenants and undertakings made by LaBranche and Cowen to each other. If any of the assumptions, representations, covenants or undertakings is incorrect, incomplete, inaccurate or is violated, the validity of the conclusions reached by counsel in their opinions could be jeopardized and the tax consequences of the merger and the second-step merger, taken together, could differ materially from those described in this joint proxy statement/prospectus. Neither Cowen nor LaBranche is currently aware of any facts or circumstances that would cause the assumptions, representations, covenants and undertakings to be incorrect, incomplete, inaccurate or violated.

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        An opinion of counsel represents counsel's legal judgment but is not binding on the IRS or any court, so there can be no certainty that the IRS will not challenge the conclusions reflected in the opinions or that a court would not sustain such a challenge. Neither Cowen nor LaBranche intends to obtain a ruling from the IRS on the tax consequences of the merger or the second-step merger. If the IRS were to successfully challenge the "reorganization" status of the merger and the second-step merger, taken together, the tax consequences would be very different from those set forth in this joint proxy statement/prospectus.

        Based on those opinions, in the event that the merger and the second-step merger, taken together, are treated for U.S. federal income tax purposes as a "reorganization" within the meaning of Section 368(a) of the Code, each of LaBranche and Cowen will be a party to the reorganization within the meaning of Section 368(b) of the Code. None of LaBranche, Cowen, Merger Sub or Merger Sub LLC will recognize any gain or loss for U.S. federal income tax purposes as a result of the merger and the second-step merger, taken together.

        You should read the section titled "Material U.S. Federal Income Tax Consequences" beginning on page 112 for a more complete discussion of the U.S. federal income tax consequences of the merger and the second-step merger. Tax matters can be complicated, and the tax consequences of the merger and the second-step merger to you will depend on your particular tax situation. You should consult your tax advisor to determine the tax consequences to you of the merger and the second-step merger.

Recommendation of LaBranche's Board of Directors (see page 64)

        After careful consideration, the LaBranche board of directors unanimously approved the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the merger, are advisable and in the best interests of LaBranche and its stockholders. For more information regarding the factors considered by the LaBranche board of directors in reaching its decision to approve and adopt the merger agreement and the merger, see the section entitled "The Merger- LaBranche's Reasons for the Merger; Recommendation of LaBranche's Board of Directors." The LaBranche board of directors unanimously recommends that LaBranche stockholders vote "FOR" the proposal to approve and adopt the merger agreement and approve the merger at the LaBranche special meeting and "FOR" the proposal to adjourn the LaBranche special meeting, if necessary, to solicit additional proxies.

Recommendation of Cowen's Board of Directors (see page 78)

        After careful consideration, the Cowen board of directors unanimously approved the merger agreement and determined that the merger agreement and the transactions contemplated thereby, including the Cowen stock issuance, are in the best interests of Cowen and its stockholders. For more information regarding the factors considered by the Cowen board of directors in reaching its decision to approve the merger agreement and to authorize the Cowen stock issuance, see the section entitled "The Merger—Cowen's Reasons for the Merger; Recommendation of Cowen's board of directors." The Cowen board of directors unanimously recommends that Cowen stockholders vote "FOR" the proposal to approve the Cowen stock issuance and "FOR" the proposal to adjourn the Cowen special meeting, if necessary, to solicit additional proxies.

Opinion of LaBranche's Financial Advisor (see page 68)

        On February 16, 2011, the LaBranche board of directors held a meeting to evaluate the proposed merger of LaBranche with a newly formed merger subsidiary of Cowen. At this meeting, Keefe, Bruyette & Woods, Inc. (which we refer to as KBW) reviewed the financial aspects of the proposed merger and rendered an oral opinion (subsequently confirmed in writing), to the LaBranche board of directors that, as of such date, and based upon and subject to factors and assumptions set forth in such

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opinion, the exchange ratio in the merger was fair, from a financial point of view, to the stockholders of LaBranche. The full text of KBW's written opinion, dated February 16, 2011, which sets forth the assumptions made, procedures followed, matters considered and limitations on the review undertaken in connection with the opinion, is attached as Annex B to this joint proxy statement/prospectus. This summary is qualified in its entirety by reference to the full text of such opinion. LaBranche's stockholders are urged to read the opinion in its entirety. KBW's opinion speaks only as of the date of the opinion. The opinion is directed to the LaBranche board and addresses only the fairness, from a financial point of view to the stockholders of LaBranche, of the exchange ratio in the merger. It does not address the underlying business decision to proceed with the merger and does not constitute a recommendation to any LaBranche stockholder as to how the stockholder should vote at the LaBranche special meeting on the merger or any related matter.

         For a more complete description, see "The Merger—Opinion of LaBranche's Financial Advisor" beginning on page 68. See also Annex B to this joint proxy statement/prospectus.

Opinion of Cowen's Financial Advisor (see page 79)

        In connection with the merger, the Cowen board of directors received an opinion, dated February 16, 2011, from Cowen's financial advisor, Sandler O'Neill + Partners, L.P. (which we refer to as Sandler O'Neill), as to the fairness of the exchange ratio paid to LaBranche from a financial point of view. The full text of Sandler O'Neill's opinion is attached as Annex C to this joint proxy statement/prospectus. The opinion outlines the procedures followed, assumptions made, matters considered and qualifications and limitations on the review undertaken by Sandler O'Neill in rendering its opinion. This summary is qualified in its entirety by reference to the full text of such opinion. Cowen's and LaBranche's stockholders are urged to read the entire opinion carefully in connection with their consideration of the transactions. Sandler O'Neill's opinion speaks only as of the date of the opinion. The opinion was directed to Cowen's board and is directed only to the fairness of the exchange ratio paid to LaBranche from a financial point of view. It does not address the underlying business decision of Cowen to engage in the transactions or any other aspect of the transactions and is not a recommendation to any Cowen stockholder as to how such stockholder should vote at the special meeting with respect to the Cowen stock issuance or any other matter.

         For a more complete description, see "The Merger—Opinion of Cowen's Financial Advisor" beginning on page 79. See also Annex C to this joint proxy statement/prospectus.

Interests of LaBranche Directors and Executive Officers in the Merger (see page 76)

        Executive officers and members of LaBranche's board of directors have interests in the merger that may be different from, or in addition to, the interests of LaBranche stockholders generally. Certain of LaBranche's executive officers have agreements with LaBranche that provide for severance benefits if their employment is terminated under certain circumstances following a change in control of LaBranche, such as the merger.

        Additionally, as detailed below under "Board of Directors and Management Following the Merger," some of LaBranche's executive officers and members of LaBranche's board of directors will continue to serve as officers or directors of the combined company upon completion of the merger. Specifically, George M.L. LaBranche, IV, LaBranche's current Chairman of the board, President and Chief Executive Officer will become a senior managing director of, and a member of the board of directors of, Cowen, Katherine E. "Wendy" Dietze will become a member of the board of directors of Cowen and William H. Burke, III, LaBranche's Chief Operating Officer, will become a senior managing director of Cowen.

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        The LaBranche board of directors was aware of these interests and considered them, among other matters, in approving the merger agreement and in recommending that you vote for the proposal to adopt the merger agreement.

Board of Directors and Management Following the Merger (see page 88)

        Effective as of the closing of the merger, the board of directors of Cowen will consist of the following eight members: (i) the six directors of Cowen immediately prior to the merger, (ii) George M.L. LaBranche, IV (the current Chairman, Chief Executive Officer and President of LaBranche) and (iii) Katherine Elizabeth Dietze (a current director of LaBranche).

        Upon completion of the merger, Mr. LaBranche will also serve as a Senior Managing Director of Cowen. William "Chip" Burke, III, Chief Operating Officer of LaBranche, will also join Cowen as a Senior Managing Director.

Regulatory Clearances Required for the Merger (see page 89)

        LaBranche and Cowen have each agreed to use their reasonable best efforts to obtain all regulatory approvals required to complete the transactions contemplated by the merger agreement. These approvals include approval from the SEC, the Financial Industry Regulatory Authority (which we refer to as FINRA), the Financial Services Authority in the United Kingdom, the Securities and Futures Commission of Hong Kong, the Department of Justice, the Federal Trade Commission and various other federal, state and foreign regulatory authorities and self-regulatory organizations.

        LaBranche and Cowen have completed, or will shortly complete, the filing of applications and notifications to obtain the required regulatory approvals. Although LaBranche and Cowen believe that the transactions do not raise substantial regulatory concerns and that all requisite regulatory approvals can be obtained on a timely basis, LaBranche and Cowen cannot be certain when or if these approvals will be obtained.

Treatment of LaBranche Stock Options and Other Stock Awards (see page 90)

        Upon completion of the merger, each of the 230,000 outstanding options to purchase LaBranche common stock granted pursuant to the previously terminated Amended and Restated LaBranche & Co Inc. 1999 Equity Incentive Plan will be cancelled for no consideration. LaBranche will also take all steps necessary to cause the LaBranche & Co Inc. 2010 Equity Incentive Plan to be terminated no later than the completion of the merger.

Completion of the Merger (see page 94)

        LaBranche and Cowen currently expect the closing of the merger to occur by the end of the second quarter or the beginning of the third quarter of 2011. However, the merger is subject to various regulatory clearances and the satisfaction or waiver of other conditions as described in the merger agreement, and it is possible that factors outside the control of LaBranche and Cowen could result in the merger being completed at an earlier time, a later time or not at all.

No Solicitation of Alternative Proposals (see page 99)

        The merger agreement precludes LaBranche and Cowen from soliciting or engaging in discussions or negotiations with a third party with respect to a proposal for a competing transaction, including the acquisition of a significant interest in Cowen's or LaBranche's common stock or assets. However, if LaBranche or Cowen receives an unsolicited proposal from a third party for a competing transaction that Cowen's or LaBranche's board of directors, as applicable, among other things, determines in good faith constitutes, or would reasonably be expected to lead to, a proposal that is superior to the

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transactions contemplated by the merger agreement, LaBranche or Cowen, as applicable, may furnish non-public information to and enter into discussions with, and only with, that third party regarding such competing transaction.

Conditions to Completion of the Merger (see page 104)

        The obligations of each of LaBranche and Cowen to effect the merger are subject to the satisfaction, or waiver, of the following conditions:

•

the approval and adoption of the merger agreement and approval of the merger by holders of a majority of the outstanding shares of LaBranche common stock at the LaBranche special meeting;



•

the approval of the Cowen stock issuance by holders of a majority of the outstanding shares of Cowen Class A common stock present in person or represented by proxy and entitled to vote thereon at the Cowen special meeting;



•

the absence of any order, injunction or regulation by a court or other governmental entity that makes illegal or prohibits the consummation of the merger, provided, however, this condition will not be available to any party whose failure to fulfill its obligations under the merger agreement regarding cooperation in preparing and filing all necessary documentation in connection with the receipt of all required third party and governmental entity consents and approvals as described under the section titled "The Merger Agreement—Efforts to Complete the Merger";



•

the waiting period (and any extension thereof) applicable to the merger under the antitrust laws of the United States having expired or been earlier terminated;



•

the shares of Cowen Class A common stock to be issued to LaBranche stockholders pursuant to the merger having been approved for quotation or listing on the NASDAQ Global Market System; and



•

the effectiveness of the registration statement of which this joint proxy statement/prospectus forms a part and the absence of a stop order or proceedings threatened or initiated by the SEC for that purpose.

        In addition, the obligations of LaBranche to effect the merger are subject to the satisfaction, or waiver, of the following additional conditions:

•

the representations and warranties of Cowen relating to capital structure being true and correct in all respects (other than immaterial misstatements or omissions) as of the date of the merger agreement and as of the date of the closing of the merger (other than those representations and warranties that were made only as of an earlier date, which need only be true and correct as of that date);



•

the representations and warranties of Cowen relating to the absence of certain changes and events and the requisite stockholder vote being true and correct in all respects, as of the date of the merger agreement and as of the date of the closing of the merger (other than those representations and warranties that were made only as of an earlier date, which need only be true and correct as of that date);



•

all other representations and warranties of Cowen being true and correct both as of the date of the merger agreement and as of the date of the closing of the merger (other than those representations and warranties that were made only as of an earlier date, which need only be true and correct as of that date), other than where the failure of these representations and warranties to be true and correct (without giving effect to any materiality qualifications

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contained in such representations and warranties) does not have, and would not reasonably be expected to have, individually or in the aggregate, a material adverse effect on Cowen;

•

Cowen having performed or complied with, in all material respects, all its agreements and covenants under the merger agreement at or prior to the consummation of the merger;



•

receipt of a certificate executed by the chief executive officer and chief financial officer of Cowen certifying as to the satisfaction of the conditions described in the preceding four bullets;



•

the non-occurrence of any event or development having a material adverse effect on Cowen since February 16, 2011;



•

the receipt, and continued validity, of all required governmental entity consents and approvals, as well as the expiration of all statutory waiting periods in respect thereof; and



•

receipt of a written opinion from Weil, Gotshal & Manges LLP to the effect that the merger and the second-step merger, taken together, will be treated as a "reorganization" within the meaning of Section 368(a) of the Code.

        In addition, the obligations of Cowen to effect the merger are subject to the satisfaction, or waiver, of the following additional conditions:

•

LaBranche has, as of the business day immediately prior to the closing of the merger, (i) a Company Consolidated Tangible Book Equity Value (as such term is defined in the merger agreement) of at least $193,000,000, (ii) a ratio of the aggregate value of the assets reflected on its unaudited balance sheet to its Company Consolidated Tangible Book Equity Value of no greater than 4.5:1, and (iii) assets reflected on its unaudited balance sheet of no more than $920,000,000 in the aggregate;



•

the representations and warranties of LaBranche relating to capital structure, other than the representations described in the preceding bullet, being true and correct in all respects (other than immaterial misstatements or omissions) as of the date of the merger agreement and as of the date of the closing of the merger (other than those representations and warranties that were made only as of an earlier date, which need only be true and correct as of that date);



•

the representations and warranties of LaBranche relating to the absence of certain changes and events and the requisite stockholder vote being true and correct in all respects, as of the date of the merger agreement and as of the date of the closing of the merger (other than those representations and warranties that were made only as of an earlier date, which need only be true and correct as of that date);



•

all other representations and warranties of LaBranche being true and correct both as of the date of the merger agreement and as of the date of the closing of the merger (other than those representations and warranties that were made only as of an earlier date, which need only be true and correct as of that date), other than where the failure of these representations and warranties to be true and correct (without giving effect to any materiality qualifications contained in such representations and warranties) does not have, and would not reasonably be expected to have, individually or in the aggregate, a material adverse effect on LaBranche;



•

LaBranche having performed or complied with, in all material respects, all its agreements and covenants under the merger agreement at or prior to the consummation of the merger;



•

receipt of a certificate executed by the chief executive officer and chief financial officer of LaBranche certifying as to the satisfaction of the conditions described in the preceding five bullets;

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•

receipt of a written opinion from Willkie Farr & Gallagher LLP to the effect that the merger and the second-step merger, taken together, will be treated as a "reorganization" within the meaning of Section 368(a) of the Code;



•

the non-occurrence of any event or development having a material adverse effect on LaBranche since February 16, 2011; and



•

the receipt, and continued validity, of all required governmental entity consents and approvals, as well as the expiration of all statutory waiting periods in respect thereof.

Termination of the Merger Agreement (see page 106)

        The merger agreement may be terminated at any time prior to the effective time of the merger, and, except as described below, whether before or after the receipt of the required stockholder approvals, under the following circumstances:

•

by mutual written consent of LaBranche and Cowen;



•

by either LaBranche or Cowen:



•

if the merger is not consummated by August 31, 2011; provided, however, that this right to terminate the merger agreement will not be available to any party whose failure to fulfill any obligation under the merger agreement has been the primary cause of the failure to close by the termination date;



•

if any governmental entity issues a final and nonappealable order, decree or ruling or taken any other action permanently restraining, enjoining or otherwise prohibiting or making illegal the consummation of the merger or any other transaction contemplated by the merger agreement, provided, that the party seeking to terminate pursuant to this right used its commercially reasonable efforts to remove such remove such restraint or prohibition; and that this right to terminate the merger agreement will not be available to any party whose breach of any provision of the merger agreement results in the imposition of such order, decree or ruling or the failure of such order, decree or ruling to be resisted, resolved or lifted;



•

if the LaBranche stockholders fail to approve and adopt the merger agreement and approve the merger at the LaBranche special meeting;



•

if the Cowen stockholders fail to approve the Cowen stock issuance at the Cowen special meeting;



•

by Cowen if (i) prior to the LaBranche special meeting the board of directors of LaBranche withdraws or adversely changes its recommendation of the merger agreement or the merger, (ii) LaBranche fails to call or hold the LaBranche special meeting, or (iii) LaBranche intentionally and materially breaches any of its obligations under the merger agreement regarding third-party acquisition proposals as described under the section titled "The Merger Agreement—No Solicitation of Alternative Proposals";



•

by LaBranche if (i) prior to the Cowen special meeting the board of directors of Cowen withdraws or adversely changes its recommendation of the Cowen stock issuance, (ii) Cowen fails to call or hold the Cowen special meeting, or (iii) Cowen intentionally and materially breaches any of its obligations under the merger agreement regarding third-party acquisition proposals as described under the section titled "The Merger Agreement—No Solicitation of Alternative Proposals";



•

by LaBranche upon a breach of any representation, warranty, covenant or agreement on the part of Cowen contained in the merger agreement such that the conditions to LaBranche's

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obligations to complete the merger are not satisfied and that either (i) the breach is not reasonably capable of being cured or (ii) in the case of a breach of a covenant or agreement, if such breach is reasonably capable of being cured, such breach has not been cured prior to the earlier of (a) 30 days following notice of such breach or (b) the termination date. However, LaBranche does not have this right to terminate the merger agreement if it is then in material breach of any of its representations, warranties, covenants or agreements contained in the merger agreement;

•

by Cowen upon a breach of any representation, warranty, covenant or agreement on the part of LaBranche contained in the merger agreement such that the conditions to Cowen's obligations to complete the merger are not satisfied and that either (i) the breach is not reasonably capable of being cured or (ii) in the case of a breach of a covenant or agreement, if such breach is reasonably capable of being cured, such breach has not been cured prior to the earlier of (a) 30 days following notice of such breach or (b) the termination date. However, Cowen does not have this right to terminate the merger agreement if it is then in material breach of any of its representations, warranties, covenants or agreements contained in the merger agreement;



•

by LaBranche if, concurrently, it (i) enters into a definitive agreement with respect to a superior proposal after complying with its applicable obligations under the merger agreement regarding third-party acquisition proposals as described under the section titled "The Merger Agreement—No Solicitation of Alternative Proposals", and (ii) pays Cowen a termination fee of $6,250,000.

Termination Fees and Expenses (see page 108)

        Generally, all fees and expenses incurred in connection with the negotiation and completion of the transactions contemplated by the merger agreement will be paid by the party incurring those expenses, subject to the specific exceptions discussed in the merger agreement. Upon termination of the merger agreement under qualifying circumstances, LaBranche or Cowen, as the case may be, will be required to pay the other party a termination fee of $6,250,000 in certain circumstances and, in certain other circumstances, expenses of the other party up to $1,500,000. See the section titled "The Merger Agreement—Termination Fees and Expenses; Liability for Breach" beginning on page 108 for a more complete discussion of the circumstances under which LaBranche or Cowen may be required to pay the termination fee and expenses.

Accounting Treatment (see page 115)

        Cowen prepares its financial statements in accordance with accounting principles generally accepted in the United States of America (which we refer to as GAAP). The merger will be accounted for by Cowen using the acquisition method of accounting. Cowen will allocate the purchase price to the fair value of LaBranche's tangible and intangible assets and liabilities at the acquisition date, with the excess/shortfall purchase price being recorded as goodwill/gain on bargain purchase.

No Appraisal Rights (see page 140)

        Appraisal rights are statutory rights that enable stockholders to dissent from an extraordinary transaction, such as a significant business combination, and to demand that the corporation pay the fair value for their shares as determined by a court in a judicial proceeding instead of receiving the consideration offered to stockholders in connection with the extraordinary transaction. Under Delaware law, holders of LaBranche common stock are not entitled to dissenters' appraisal rights in connection with the merger. Since Cowen is not a party to the merger, holders of Cowen Class A common stock are also not entitled to dissenters' appraisal rights in connection with the merger under Delaware law. See the section entitled "No Appraisal Rights" beginning on page 140.

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Comparison of Stockholder Rights and Corporate Governance Matters ( see page 134)

        LaBranche stockholders receiving merger consideration will have different rights once they become stockholders of Cowen due to differences between the governing corporate documents of LaBranche and the governing corporate documents of Cowen. These differences are described in detail under the section entitled "Comparison of Rights of LaBranche Stockholders and Cowen Stockholders" beginning on page 134.

Listing of Cowen Class A common stock; Delisting and Deregistration of LaBranche Common Stock (see page 91)

        It is a condition to the completion of the merger that the shares of Cowen Class A common stock to be issued to LaBranche stockholders pursuant to the merger be authorized for listing on the NASDAQ Global Market System (or any successor inter-dealer quotation system or stock exchange thereto) at the effective time of the merger. Upon completion of the merger, shares of LaBranche common stock currently listed on the New York Stock Exchange will cease to be listed on the New York Stock Exchange and will be subsequently deregistered under the Exchange Act.

Voting Agreements (see page 110)

        Each of George M.L. LaBranche, IV (Chairman, Chief Executive Officer and President of LaBranche), Alfred O. Hayward, Jr. (Executive Vice President of LaBranche) and William J. Burke, III (Chief Operating Officer of LaBranche) has entered into an agreement with Cowen to vote all of the shares of LaBranche common stock owned by that individual at the time of the LaBranche special meeting in favor of approval and adoption of the merger agreement and approval of the merger. In addition, Messrs. LaBranche and Hayward have agreed to direct the parties to the LaBranche stockholders' agreement, to vote all of their shares in favor of approval and adoption of the merger agreement and approval of the merger. Collectively, at the close of business for the record date for the LaBranche special meeting, Messrs. LaBranche, Burke and Hayward and the other LaBranche stockholders party to the LaBranche stockholders' agreement held approximately 14.7% of the outstanding shares of LaBranche common stock.

        RCG has entered into an agreement with LaBranche to vote all of the shares of Cowen Class A common stock owned by RCG at the time of the Cowen special meeting in favor of the Cowen stock issuance. At the close of business for the record date for the Cowen special meeting, RCG held approximately 43.1% of the issued and outstanding Cowen Class A common stock.

The Meetings

The LaBranche Special Meeting ( see page 48)

        The special meeting of LaBranche stockholders is scheduled to be held at the Down Town Association, 60 Pine Street, New York, New York 10005 on June 15, 2011, at 9:00 a.m., local time. The special meeting of LaBranche's stockholders is being held in order to consider and vote on:

•

the proposal to approve and adopt the merger agreement and approve the merger;



•

the proposal to adjourn the LaBranche special meeting, if necessary or appropriate, to solicit additional proxies if there are not sufficient votes to approve the foregoing proposal.

        Only holders of record of LaBranche common stock at the close of business on May 4, 2011, the record date for the LaBranche special meeting, are entitled to notice of, and to vote at, the LaBranche special meeting or any adjournments or postponements thereof. At the close of business on the record date, 40,931,997 shares of LaBranche common stock were outstanding, approximately 13.0% of which were held by LaBranche's directors and executive officers.

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        Three of LaBranche's directors and executive officers, George M.L. LaBranche IV, William J. Burke, III and Alfred O. Hayward, Jr., have entered into a voting agreement with Cowen pursuant to which they have agreed to, among other things, vote all of their shares in favor of approval and adoption of the merger agreement and approval of the merger. In addition, Messrs. LaBranche and Hayward have agreed to direct the parties to the LaBranche stockholders' agreement to vote all of their shares in favor of approval and adoption of the merger agreement and approval of the merger. Collectively, at the close of business on the record date for the LaBranche special meeting, Messrs. LaBranche, Burke and Hayward and the parties to the LaBranche stockholders' agreement held approximately 14.7% of the outstanding shares of LaBranche common stock. LaBranche currently expects that LaBranche's remaining directors and executive officers, who are not party to the voting agreement, will vote their shares in favor of the proposal to adopt the merger agreement, although none of them has entered into any agreement obligating them to do so.

        You may cast one vote for each share of LaBranche common stock you own. The proposal to approve and adopt the merger agreement and approve the merger requires the affirmative vote of the holders of a majority of the outstanding shares of LaBranche common stock. If it is necessary or appropriate to solicit additional proxies if there are not sufficient votes to approve the proposal to approve and adopt the merger agreement and approve the merger, the LaBranche stockholders, by the affirmative vote of holders of a majority of the outstanding shares of LaBranche common stock present in person or represented by proxy at the LaBranche special meeting and entitled to vote, whether or not a quorum is present, may adjourn the meeting to another time or place without notice other than announcement at the meeting unless the adjournment is for more than 30 days or if after the adjournment a new record date is fixed for the adjourned meeting, in which case a notice of the adjourned meeting shall be given to each stockholder of record entitled to vote at the meeting.

The Cowen Special Meeting ( see page 52)

        The special meeting of Cowen stockholders will be held at The InterContinental The Barclay, Park Avenue Room, 111 East 48th Street, New York, New York 10017 on June 15, 2011, at 3:00 p.m., local time. The special meeting of Cowen stockholders is being held to consider and vote on:

•

the proposal to approve the Cowen stock issuance; and



•

the proposal to adjourn the Cowen special meeting, if necessary, to solicit additional proxies if there are not sufficient votes at the time of the special meeting to approve the foregoing proposal.

        Completion of the merger is conditioned on approval of the Cowen stock issuance.

        Only holders of record of Cowen Class A common stock at the close of business on May 4, 2011, the record date for the Cowen special meeting, are entitled to vote at the Cowen special meeting or any adjournments or postponements thereof. At the close of business on the record date, 75,665,037 shares of Cowen Class A common stock were issued and outstanding.

        RCG has entered into an agreement with LaBranche to vote all of the shares of Cowen Class A common stock owned by RCG at the time of the Cowen special meeting in favor of the Cowen stock issuance. At the close of business for the record date for the Cowen special meeting, RCG held approximately 43.1% of the issued and outstanding Cowen Class A common stock.

        You may cast one vote for each share of Cowen Class A common stock you own. The proposal to approve the Cowen stock issuance requires the affirmative vote of holders of a majority of the outstanding shares of Cowen capital stock present in person or represented by proxy and entitled to vote on the proposal. If necessary to solicit additional proxies if there are not sufficient votes to approve the Cowen stock issuance, the holders of a majority of the shares of Cowen Class A common stock entitled to vote and present in person or by proxy, whether or not a quorum is present, may

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adjourn the Cowen special meeting to another time or place without further notice unless the adjournment is for more than 30 days or if after the adjournment a new record date is fixed for the adjourned meeting, in which case a notice of the adjourned meeting shall be given to each Cowen stockholder of record entitled to vote at the Cowen special meeting.

Voting by LaBranche and Cowen Directors and Executive Officers (see pages 51 and 54)

        On the record date for the LaBranche special meeting, the directors and executive officers of LaBranche and their affiliates (excluding Messrs. LaBranche, Hayward and Burke) owned and were entitled to vote 205,156 shares of LaBranche's common stock, representing approximately .5% of the outstanding LaBranche common stock. Each of George M.L. LaBranche, IV (Chairman, Chief Executive Officer and President of LaBranche), Alfred O. Hayward, Jr. (Executive Vice President of LaBranche) and William J. Burke, III (Chief Operating Officer of LaBranche) has entered into an agreement with Cowen to vote all of the shares of LaBranche common stock owned by that individual at the time of the LaBranche special meeting in favor of approval and adoption of the merger agreement and approval of the merger. In addition, Messrs. LaBranche and Hayward have agreed to direct the parties to the LaBranche stockholders' agreement, to, among other things, vote all of their shares in favor of approval and adoption of the merger agreement and approval of the merger. Collectively, at the close of business for the record date for the LaBranche special meeting, Messrs. LaBranche, Burke and Hayward and the other LaBranche stockholders party to the LaBranche stockholders' agreement held approximately 14.7% of the outstanding shares of LaBranche common stock. For more details, see "Voting Agreements" beginning on page 110.

        On the record date for the Cowen special meeting, the directors and executive officers of Cowen and their affiliates owned and were entitled to vote 33,031,574 shares of Cowen's Class A common stock, representing 43.7% of the outstanding Cowen Class A common stock.

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Selected Historical Consolidated Financial Data

Selected Consolidated Historical Financial Data of LaBranche

        The following table presents LaBranche's selected historical consolidated financial data as of and for the years ended December 31, 2010, 2009, 2008, 2007, and 2006. You should read this information in conjunction with LaBranche's consolidated financial statements and related notes included in LaBranche's Annual Report on Form 10-K for the fiscal year ended December 31, 2010, which is incorporated by reference in this document and from which this information is derived. See the section titled "Where You Can Find More Information" beginning on page 143.

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Selected Consolidated Historical Financial Data of Cowen

        The following table presents Cowen's selected historical consolidated financial data as of and for the years ended December 31, 2010, 2009, 2008, 2007 and 2006. You should read this information in conjunction with Cowen's consolidated financial statements and related notes included in Cowen's Annual Report on Form 10-K for the fiscal year ended December 31, 2010 which is incorporated by reference in this document and from which this information is derived. See the section titled "Where You Can Find More Information" beginning on page 143.

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