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	<periodOfReport>2003-06-30</periodOfReport>
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    <issuer>
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        <issuerName>GENZYME CORP</issuerName>
        <issuerTradingSymbol>GENZ</issuerTradingSymbol>
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	<reportingOwner>
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            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
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			<isOfficer>1</isOfficer>
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			<isOther>0</isOther>
			<officerTitle>Executive Vice President</officerTitle>
		</reportingOwnerRelationship>
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		<securityTitle>
			<value>Biosurgery ISO stock option (right to buy)</value>
		</securityTitle>
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			<value>52.21</value>
		</conversionOrExercisePrice>
		<transactionDate>
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				<value>Genzyme Biosurgery common stock (GZBX)</value>
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			<natureOfOwnership>
				<value/>
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	<derivativeSecurity>
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		</conversionOrExercisePrice>
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			<underlyingSecurityTitle>
				<value>Genzyme Biosurgery common stock (GZBX)</value>
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			<natureOfOwnership>
				<value/>
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	</derivativeSecurity>
	<derivativeSecurity>
		<securityTitle>
			<value>Genzyme General ISO stock option (right to buy)</value>
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		<expirationDate>
			<value>2006-01-02</value>
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		<underlyingSecurity>
			<underlyingSecurityTitle>
				<value>Genzyme General common stock (GENZ)</value>
			</underlyingSecurityTitle>
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				<value>207</value>
			</underlyingSecurityShares>
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			</sharesOwnedFollowingTransaction>
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			<directOrIndirectOwnership>
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			<natureOfOwnership>
				<value/>
			</natureOfOwnership>
		</ownershipNature>
	</derivativeSecurity>
	<derivativeSecurity>
		<securityTitle>
			<value>Genzyme General NQ stock option (right to buy)</value>
		</securityTitle>
		<conversionOrExercisePrice>
			<value>0.00</value>
			<footnoteId id="F3"/>
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		<transactionDate>
			<value>2003-06-30</value>
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		<transactionAmounts>
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				<value>368</value>
				<footnoteId id="F1"/>
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		<exerciseDate>
			<value>2005-06-30</value>
		</exerciseDate>
		<expirationDate>
			<value>2005-12-15</value>
		</expirationDate>
		<underlyingSecurity>
			<underlyingSecurityTitle>
				<value>Genzyme General common stock (GENZ)</value>
			</underlyingSecurityTitle>
			<underlyingSecurityShares>
				<value>368</value>
			</underlyingSecurityShares>
		</underlyingSecurity>
		<postTransactionAmounts>
			<sharesOwnedFollowingTransaction>
				<value>368</value>
			</sharesOwnedFollowingTransaction>
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			<directOrIndirectOwnership>
				<value>D</value>
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				<value/>
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	<footnotes>
		<footnote id="F1">On June 30, 2003 in relation to the elimination of Genzyme's tracking stock structure, all stock options of Genzyme Biosurgery and Genzyme Molecular were exchanged for stock options of Genzyme General.  The exchange ratio was based on the closing prices of all three stocks on 6/30/03.  Genzyme Biosurgery options were exchanged at a rate of .04945 and Genzyme Molecular Oncology options were exchanged at a rate of .05614.</footnote>
		<footnote id="F2">Options vest in 20% annual increments beginning on the original date of grant.</footnote>
		<footnote id="F3">These options have a converted exercise price of $1,055.82 per share.</footnote>
	</footnotes>
	<ownerSignature>
		<signatureName>By: Susan P. Cogswell, Attorney-in-Fact</signatureName>
		<signatureDate>2003-07-02</signatureDate>
	</ownerSignature>
</ownershipDocument>
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X0101
4
2003-06-30
0
0000732485
GENZYME CORP
GENZ
0001021041
WIRTH PETER
0
1
0
0
Executive Vice President
Biosurgery ISO stock option (right to buy)
52.21
2003-06-30
4
J
0
4190
0
D
1995-12-15
2006-01-02
Genzyme Biosurgery common stock (GZBX)
4190
0
D
Biosurgery NQ stock option (right to buy)
52.21
2003-06-30
4
J
0
7448
0
D
2005-06-30
2005-12-15
Genzyme Biosurgery common stock (GZBX)
7448
0
D
Genzyme General ISO stock option (right to buy)
0.00
2003-06-30
4
J
0
207
0
A
1995-12-15
2006-01-02
Genzyme General common stock (GENZ)
207
207
D
Genzyme General NQ stock option (right to buy)
0.00
2003-06-30
4
J
0
368
0
A
2005-06-30
2005-12-15
Genzyme General common stock (GENZ)
368
368
D
On June 30, 2003 in relation to the elimination of Genzyme's tracking stock structure, all stock options of Genzyme Biosurgery and Genzyme Molecular were exchanged for stock options of Genzyme General.  The exchange ratio was based on the closing prices of all three stocks on 6/30/03.  Genzyme Biosurgery options were exchanged at a rate of .04945 and Genzyme Molecular Oncology options were exchanged at a rate of .05614.
Options vest in 20% annual increments beginning on the original date of grant.
These options have a converted exercise price of $1,055.82 per share.
By: Susan P. Cogswell, Attorney-in-Fact
2003-07-02