Mutual Fund Summary Prospectus (497k)

October 26, 2012

Summary Prospectus

BlackRock Municipal Bond Fund, Inc. | Service Shares

> BlackRock National Municipal Fund

Fund

Service
Shares

BlackRock National Municipal Fund

BNMSX

Before you invest, you may want to review the Fund’s prospectus, which contains more information about the Fund and its risks. You can find the Fund’s prospectus (including amendments and supplements) and other information about the Fund, including the Fund’s statement of additional information and shareholder report, online at http://www.blackrock.com/prospectus. You can also get this information at no cost by calling (800) 441-7762 or by sending an e-mail request to prospectus.request@blackrock.com , or from your financial professional. The Fund’s prospectus and statement of additional information, both dated October 26, 2012, as amended and supplemented from time to time, are incorporated by reference into (legally made a part of) this Summary Prospectus.

This Summary Prospectus contains information you should know before investing, including information about risks. Please read it before you invest and keep it for future reference.

The Securities and Exchange Commission has not approved or disapproved these securities or passed upon the adequacy of this Summary Prospectus. Any representation to the contrary is a criminal offense.

Not FDIC Insured • No Bank Guarantee • May Lose Value

Summary Prospectus

Key Facts about BlackRock National Municipal Fund

Investment Objective

The investment objective of the BlackRock National Municipal Fund (the “Fund”) is to provide shareholders with as high a level of income exempt from Federal income taxes as is consistent with the investment policies of the Fund.

Fees and Expenses of the Fund

This table describes the fees and expenses that you may pay if you buy and hold Service Shares of the Fund.

Shareholder Fees (fees paid directly from your investment)				Service Shares
Maximum Sales Charge (Load) Imposed on Purchases (as percentage of offering price)				None
Maximum Deferred Sales Charge (Load) (as percentage of offering price or redemption proceeds, whichever is lower)				None

Annual Fund Operating Expenses (expenses that you pay each year as a percentage of the value of your investment)				Service Shares
Management Fee				0.48%
Distribution and/or Service (12b-1) Fees				0.25%
Other Expenses				0.18%
Interest Expense				0.08%
Miscellaneous Other Expenses				0.10%
Acquired Fund Fees and Expenses ¹				0.02%
Total Annual Fund Operating Expenses ¹				0.93%

The Total Annual Fund Operating Expenses do not correlate to the ratio of expenses to average net assets given in the Fund’s most recent annual report, which does not include Acquired Fund Fees and Expenses.

Example:

This Example is intended to help you compare the cost of investing in the Fund with the cost of investing in other mutual funds. The Example assumes that you invest $10,000 in the Fund for the time periods indicated and then redeem all of your shares at the end of those periods. The Example also assumes that your investment has a 5% return each year and that the Fund’s operating expenses remain the same. Although your actual costs may be higher or lower, based on these assumptions your costs would be:

				1 Year				3 Years				5 Years				10 Years
Service Shares				$	95			$	296			$	515			$	1,143

Portfolio Turnover:

The Fund pays transaction costs, such as commissions, when it buys and sells securities (or “turns over” its portfolio). A higher portfolio turnover may indicate higher transaction costs and may result in higher taxes when shares are held in a taxable account. These costs, which are not reflected in annual fund operating expenses or in the example, affect the Fund’s performance. During the most recent fiscal year, the Fund’s portfolio turnover rate was 39% of the average value of its portfolio.

Principal Investment Strategies of the Fund

Under normal circumstances, the Fund seeks to achieve its objective by investing at least 80% of its assets in municipal bonds. Municipal bonds include debt obligations issued by or on behalf of a governmental entity or other qualifying issuer that pay interest that is, in the opinion of bond counsel to the issuer, generally excludable from gross income for Federal income tax purposes (except that the interest may be includable in taxable income for purposes of the Federal alternative minimum tax). Municipal bonds may be obligations of a variety of issuers, including governmental entities or other qualifying issuers. Issuers may be states, territories and possessions of the United States and the District of Columbia and their political subdivisions, agencies and instrumentalities. Municipal bonds also include short-term tax-exempt obligations like municipal notes and variable rate demand obligations.

The Fund may invest in municipal bonds rated in any rating category or in unrated municipal bonds. Although Fund management presently intends to invest at least 65% of the Fund’s net assets in municipal bonds rated investment grade or in unrated municipal bonds that Fund management believes are of comparable quality, it is possible that in the future the Fund could invest up to 100% of its assets in “junk bonds.” Investment grade bonds are securities which are rated in the four highest categories by at least one of the major rating agencies or determined by the management team to be of similar quality. The Fund does not intend to invest more than 35% of its net assets in junk bonds or in unrated bonds that Fund management believes are of comparable quality. This is a non-fundamental policy and may be changed by the Board at any time. The Fund will usually invest in municipal bonds that have a maturity of five years or longer.

The Fund may engage in transactions in certain derivatives, such as financial futures contracts and options thereon, indexed and inverse floating rate obligations and swap agreements, including credit default swap agreements. The Fund may use derivative instruments to hedge its investments or to seek to enhance returns. The Fund may invest in tender option bonds and residual interest tender option bonds, and may also invest in securities the return of which is inversely related to changes in an interest rate (“inverse floaters”). The Fund will look through to the underlying municipal bond held by a tender option bond trust for purposes of the Fund’s 80% policy.

Principal Risks of Investing in the Fund

Risk is inherent in all investing. The value of your investment in the Fund, as well as the amount of return you receive on your investment, may fluctuate significantly from day to day and over time. You may lose part or all of your investment in the Fund or your investment may not perform as well as other similar investments. The following is a summary description of principal risks of investing in the Fund.

Credit Risk — Credit risk refers to the possibility that the issuer of a security will not be able to make payments of interest and principal when due. Changes in an issuer’s credit rating or the market’s perception of an issuer’s creditworthiness may also affect the value of the Fund’s investment in that issuer.

Derivatives Risk — The Fund’s use of derivatives may reduce the Fund’s returns and/or increase volatility. Volatility is defined as the characteristic of a security, an index or a market to fluctuate significantly in price within a short time period. Derivatives are also subject to counterparty risk, which is the risk that the other party in the transaction will not fulfill its contractual obligation. A risk of the Fund’s use of derivatives is that the fluctuations in their values may not correlate perfectly with the overall securities markets. The possible lack of a liquid secondary market for derivatives and the resulting inability of the Fund to sell or otherwise close a derivatives position could expose the Fund to losses and could make derivatives more difficult for the Fund to value accurately. Derivatives may give rise to a form of leverage and may expose the Fund to greater risk and increase its costs. Recent legislation calls for new regulation of the derivatives markets. The extent and impact of the regulation is not yet known and may not be known for some time. New regulation may make derivatives more costly, may limit the availability of derivatives, or may otherwise adversely affect the value or performance of derivatives.

Interest Rate Risk — Interest rate risk is the risk that prices of bonds and other fixed-income securities will increase as interest rates fall, and decrease as interest rates rise.

Junk Bonds Risk — Although junk bonds generally pay higher rates of interest than investment grade bonds, junk bonds are high risk investments that may cause income and principal losses for the Fund.

Leverage Risk — Some transactions may give rise to a form of economic leverage. These transactions may include, among others, derivatives, and may expose the Fund to greater risk and increase its costs. The use of leverage may cause the Fund to liquidate portfolio positions when it may not be advantageous to do so to satisfy its obligations or to meet any required asset segregation requirements. Increases and decreases in the value of the Fund’s portfolio will be magnified when the Fund uses leverage.

Liquidity Risk — Liquidity risk exists when particular investments are difficult to purchase or sell. The Fund’s investments in illiquid securities may reduce the returns of the Fund because it may be difficult to sell the illiquid securities at an advantageous time or price. To the extent that the Fund’s principal investment strategies involve derivatives or securities with substantial market and/or credit risk, the Fund will tend to have the greatest exposure to liquidity risk. Liquid investments may become illiquid after purchase by the Fund, particularly during periods of market turmoil. Illiquid investments may be harder to value, especially in changing markets, and if the Fund is forced to sell these investments to meet redemption requests or for other cash needs, the Fund may suffer a loss. In addition, when there is illiquidity in the market for certain securities, the Fund, due to limitations on illiquid investments, may be subject to purchase and sale restrictions.

Market Risk and Selection Risk — Market risk is the risk that one or more markets in which the Fund invests will go down in value, including the possibility that the markets will go down sharply and unpredictably. Selection risk is the risk that the securities selected by Fund management will underperform the markets, the relevant indices or the securities selected by other funds with similar investment objectives and investment strategies. This means you may lose money.

Municipal Securities Risks — Municipal securities risks include the ability of the issuer to repay the obligation, the relative lack of information about certain issuers of municipal securities, and the possibility of future legislative changes which could affect the market for and value of municipal securities. These risks include:

General Obligation Bonds Risks — Timely payments depend on the issuer’s credit quality, ability to raise tax revenues and ability to maintain an adequate tax base.

Revenue Bonds Risks — These payments depend on the money earned by the particular facility or class of facilities, or the amount of revenues derived from another source.

Private Activity Bonds Risks — Municipalities and other public authorities issue private activity bonds to finance development of industrial facilities for use by a private enterprise. The private enterprise pays the principal and interest on the bond, and the issuer does not pledge its faith, credit and taxing power for repayment.

Moral Obligation Bonds Risks — Moral obligation bonds are generally issued by special purpose public authorities of a state or municipality. If the issuer is unable to meet its obligations, repayment of these bonds becomes a moral commitment, but not a legal obligation, of the state or municipality.

Municipal Notes Risks — Municipal notes are shorter term municipal debt obligations. If there is a shortfall in the anticipated proceeds, the notes may not be fully repaid and the Fund may lose money.

Municipal Lease Obligations Risks — In a municipal lease obligation, the issuer agrees to make payments when due on the lease obligation. Although the issuer does not pledge its unlimited taxing power for payment of the lease obligation, the lease obligation is secured by the leased property.

Tax-Exempt Status Risk — The Fund and its investment manager will rely on the opinion of issuers’ bond counsel and, in the case of derivative securities, sponsors’ counsel, on the tax-exempt status of interest on municipal bonds and payments under derivative securities. Neither the Fund nor its investment manager will independently review the bases for those tax opinions, which may ultimately be determined to be incorrect and subject the Fund and its shareholders to substantial tax liabilities.

Prepayment and Extension Risk — When interest rates fall, an issuer may redeem a security with call features by repaying it early, and the Fund may have to invest the proceeds in securities with lower yields. When interest rates rise, certain obligations will be paid off by the issuer more slowly than anticipated, causing the value of these securities to fall.

Tender Option Bonds and Related Securities Risk — Investments in tender option bonds, residual interest tender option bonds and inverse floaters expose the Fund to the same risks as investments in derivatives, as well as risks associated with leverage, described above, especially the risk of increased volatility. An investment in these securities typically will involve greater risk than an investment in a municipal fixed rate security, including the risk of loss of principal. Distributions on residual interest tender option bonds and inverse floaters will bear an inverse relationship to short-term municipal security interest rates. Distributions on the residual interests and inverse floaters paid to the Fund will be reduced or, in the extreme, eliminated as short-term municipal interest rates rise and will increase when short-term municipal interest rates fall. Residual interest tender option bonds and inverse floaters generally will underperform the market for fixed rate municipal securities in a rising interest rate environment.

Performance Information

Service Shares commenced operations on July 18, 2011. As a result, the chart gives you a picture of the long-term performance of the Fund for Investor A Shares, which are not offered in this prospectus. Investor A Shares would have annual returns substantially similar to Service Shares differing only to the extent that Investor A and Service Shares have different expenses. The actual return of Service Shares would be similar to that of Investor A Shares because Service Shares are subject to the same distribution and/or service (12b-1) fees as Investor A Shares.

The information shows you how the Fund’s performance has varied year by year and provides some indication of the risks of investing in the Fund. The table compares the Fund’s performance to that of the S&P Municipal Bond Index. Prior to the Service Shares inception date of July 18, 2011, the returns for Service Shares are based on the Fund’s Institutional Shares adjusted to reflect the applicable distribution and service (12b-1) fees. As with all such investments, past performance (before and after taxes) is not an indication of future results. Sales charges are not reflected in the bar chart. If they were, returns would be less than those shown. However, the table includes all applicable fees and sales charges. If the Fund’s investment manager and its affiliates had not waived or reimbursed certain Fund expenses during these periods, the Fund’s returns would have been lower. Updated information on the Fund’s performance can be obtained by visiting http://www.blackrock.com/funds or can be obtained by phone at 800-882-0052.

Investor A Shares
ANNUAL TOTAL RETURNS
BlackRock National Municipal Fund
As of 12/31

During the ten-year period shown in the bar chart, the highest return for a quarter was 7.42% (quarter ended September 30, 2009) and the lowest return for a quarter was –4.66% (quarter ended December 31, 2008). The year-to-date return as of September 30, 2012 was 9.19%.

As of 12/31/11 Average Annual Total Returns	1 Year			5 Years			10 Years
BlackRock National Municipal Fund — Investor A Shares
Return Before Taxes		6.63	%		3.57	%		4.78	%
Return After Taxes on Distributions		6.63	%		3.57	%		4.78	%
Return After Taxes on Distributions and Sale of Fund Shares		5.91	%		3.67	%		4.76	%
BlackRock National Municipal Fund — Service Shares
Return Before Taxes		11.43	%		4.47	%		5.24	%
S&P Municipal Bond Index (Reflects no deduction for fees, expenses or taxes)		10.62	%		4.86	%		5.35	%

After-tax returns are calculated using the historical highest individual Federal marginal income tax rates and do not reflect the impact of state and local taxes. Actual after-tax returns depend on the investor’s tax situation and may differ from those shown, and the after-tax returns shown are not relevant to investors who hold their shares through tax-deferred arrangements such as 401(k) plans or individual retirement accounts. After-tax returns are shown for Investor A Shares only, and the after-tax returns for Service Shares will vary.

Investment Manager

The Fund’s investment manager is BlackRock Advisors, LLC (“BlackRock”). The Fund’s sub-adviser is BlackRock Investment Management, LLC. Where applicable, the use of the term BlackRock also refers to the Fund’s sub-adviser.

Portfolio Managers

Name	Portfolio Manager of the Fund Since	Title
Walter O’Connor, CFA	1996	Managing Director of BlackRock, Inc.
Theodore R. Jaeckel, CFA	2006	Managing Director of BlackRock, Inc.

Purchase and Sale of Fund Shares

You may purchase or redeem shares of the Fund each day the New York Stock Exchange (“NYSE”) is open. To purchase or sell shares you should contact your financial intermediary or financial professional, or, if you hold your shares through the Fund, you should contact the Fund by phone at (800) 537-4942, by mail (c/o BlackRock Funds, P.O. Box 9819, Providence, Rhode Island 02940-8019), or by the Internet at www.blackrock.com/funds. The Fund’s initial and subsequent investment minimums generally are as follows, although the Fund may reduce or waive the minimums in some cases:

				Service Shares
Minimum Initial Investment				$5,000
Minimum Additional Investment				There is no minimum amount for additional investments.

Tax Information

The Fund’s dividends and distributions may be subject to Federal income taxes and may be taxed as ordinary income or capital gains, unless you are a tax-exempt investor or are investing through a retirement plan, in which case you may be subject to Federal income tax upon withdrawal from such tax deferred arrangements. The Fund intends to make distributions most of which will be excludable from gross income for Federal income tax purposes.

Payments to Broker/Dealers and Other Financial Intermediaries

If you purchase shares of the Fund through a broker-dealer or other financial intermediary, the Fund and BlackRock Investments, LLC, the Fund’s distributor, or its affiliates may pay the intermediary for the sale of Fund shares and other services. These payments may create a conflict of interest by influencing the broker-dealer or other financial intermediary and your individual financial professional to recommend the Fund over another investment. Ask your individual financial professional or visit your financial intermediary’s website for more information.