- Initial Statement of Beneficial Ownership (3)

FORM 3	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES	OMB APPROVAL OMB Number: 3235-0104 Expires: February 28, 2011 Estimated average burden hours per response... 0.5
	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(h) of the Investment Company Act of 1940

1. Name and Address of Reporting Person ^*

SANOFI-AVENTIS

2. Date of Event Requiring Statement (MM/DD/YYYY) 4/5/2011

3. Issuer Name and Ticker or Trading Symbol

GENZYME CORP [GENZ]

(Last) (First) (Middle)

174, AVENUE DE FRANCE

4. Relationship of Reporting Person(s) to Issuer (Check all applicable)

_____ Director ___ X ___ 10% Owner
_____ Officer (give title below) _____ Other (specify below)

(Street)

PARIS, I0 75013

(City) (State) (Zip)

5. If Amendment, Date Original Filed (MM/DD/YYYY)

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

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

Table I - Non-Derivative Securities Beneficially Owned
1.Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)
Common Stock, $0.01 par value	184038545 ⁽¹⁾	I	By GC Merger Corp. ⁽²⁾

*Table II - Derivative Securities Beneficially Owned ( e.g.* , puts, calls, warrants, options, convertible securities)**
1. Title of Derivate Security (Instr. 4)	2. Date Exercisable and Expiration Date (MM/DD/YYYY)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivate Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security		6. Nature of Indirect Beneficial Ownership (Instr. 5)

Explanation of Responses:
( 1)	Reflects shares exchanged in an exchange offer.
( 2)	The shares are held by GC Merger Corp. (the "Purchaser"). The Purchaser is direct wholly-owned subsidiary of sanofi-aventis ("Parent") and is the owner of the shares purchased in the exchange offer. The shares may also be deemed to be indirectly beneficially owned by Parent.

Reporting Owners
Reporting Owner Name / Address	Relationships
Reporting Owner Name / Address	Director	10% Owner	Officer	Other
SANOFI-AVENTIS 174, AVENUE DE FRANCE PARIS, I0 75013		X
GC Merger Corp. 55 CORPORATE DRIVE BRIDGEWATER, NJ 08807		X

Signatures
/s/ SEE EXHIBIT 99.1		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 5(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.