FORM 4
[ ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).         
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES
                                                                                  
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public
Utility Holding Company Act of 1935 or Section 30(f) of the Investment Company Act of 1940
                      

1. Name and Address of Reporting Person *

WHITWORTH RALPH V 		2. Issuer Name and Ticker or Trading Symbol

GENZYME CORP [ GENZ ] 		5. Relationship of Reporting Person(s) to Issuer (Check all applicable)

__ X __ Director                      _____ 10% Owner
_____ Officer (give title below)      _____ Other (specify below)
(Last)          (First)          (Middle)

12400 HIGH BLUFF DR. #600 		3. Date of Earliest Transaction (MM/DD/YYYY)

4/4/2011
(Street)

SAN DIEGO, CA 92130
(City)        (State)        (Zip)
4. If Amendment, Date Original Filed (MM/DD/YYYY)

 
6. Individual or Joint/Group Filing (Check Applicable Line)

_ X _ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3) 		2. Trans. Date 2A. Deemed Execution Date, if any 3. Trans. Code
(Instr. 8) 		4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5) 		5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4) 		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Genzyme common stock (GENZ)   4/4/2011     M    2375.0000   A $0.0000   4750.0000   D    
Genzyme common stock (GENZ)   4/4/2011     D    2375.0000   D $74.0000   2375.0000   D    
Genzyme common stock (GENZ)   4/4/2011     U    10606248.0000   D $74.0000   0.0000   I   (1) see footnotes (1) and (2)   (2)

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 3) 		2. Conversion or Exercise Price of Derivative Security 3. Trans. Date 3A. Deemed Execution Date, if any 4. Trans. Code
(Instr. 8) 		5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5) 		6. Date Exercisable and Expiration Date 7. Title and Amount of Securities Underlying Derivative Security
(Instr. 3 and 4) 		8. Price of Derivative Security
(Instr. 5) 		9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Restricted Stock Units   $0.0000   4/4/2011     M         2375.0000    6/16/2011   (3)   (3) Genzyme common stock (GENZ)   2375.0000   $0.0000   0.0000   D    
Stock Option (right to buy)   $52.6600   4/4/2011     D         7125.0000    6/16/2010   (4) 4/14/2020   Genzyme common stock (GENZ)   7125.0000   $51.5200   0.0000   D    
Stock Option (right to buy)   $51.5200   4/4/2011     D         7125.0000    6/16/2011   (4) 6/16/2020   Genzyme common stock (GENZ)   7125.0000   $52.6600   0.0000   D    

Explanation of Responses:
( 1)  The reporting person is one of the Principals of Relational Investors LLC ("RILLC"). RILLC is the record owner of 100 shares and sole general partner, or the sole managing member of the general partner, of Relational Investors, L.P., Relational Fund Partners, L.P., Relational Coast Partners, L.P., RH Fund 1, L.P., RH Fund 6, L.P., Relational Investors VIII, L.P., Relational Investors IX, L.P., Relational Investors X, L.P., Relational Investors XV, L.P., Relational Investors XVI, L.P., Relational Investors XX, L.P., Relational Investors XXII, L.P., Relational Investors XXIII, L.P., and Relational Investors Alpha Fund I, L.P.
( 2)  The Limited Partnerships in footnote 1 own a total of 7,963,166 shares. An additional 2,234,482 shares are held in accounts managed by RILLC and an additional 408,500 shares are held through co-investment arrangements with certain entities listed in footnote 1. The reporting person disclaims beneficial ownership of these securities except to the extent of his pecuniary interest therein.
( 3)  The vested restricted stock units were scheduled to vest on the date of the 2011 annual meeting of shareholders.
( 4)  This option, which provided for vesting at the next annual meeting of shareholders, was cancelled upon the consummation of the sanofi-aventis tender offer in exchange for a payment representing (A) an amount of cash equal to the excess of $74.00 over the exercise price of the option, multiplied by the total number of shares subject to such options, and (B) one contingent value right (CVR) per cancelled option.

Reporting Owners
Reporting Owner Name / Address
Relationships
Director 10% Owner Officer Other
WHITWORTH RALPH V
12400 HIGH BLUFF DR. #600
SAN DIEGO, CA 92130 		X



Signatures
Susan P. Cogswell, Attorney-in-Fact 4/6/2011
** Signature of Reporting Person Date


Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.
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