<?xml version="1.0"?>
<ownershipDocument>
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    <documentType>4</documentType>
	<periodOfReport>2003-06-30</periodOfReport>
	<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000732485</issuerCik>
        <issuerName>GENZYME CORP</issuerName>
        <issuerTradingSymbol>GENZ</issuerTradingSymbol>
	</issuer>
	<reportingOwner>
		<reportingOwnerId>
            <rptOwnerCik>0001021040</rptOwnerCik>
            <rptOwnerName>VAN HEEK G JAN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
			<isDirector>0</isDirector>
			<isOfficer>1</isOfficer>
			<isTenPercentOwner>0</isTenPercentOwner>
			<isOther>0</isOther>
			<officerTitle>Executive Vice President</officerTitle>
		</reportingOwnerRelationship>
	</reportingOwner>
	<derivativeSecurity>
		<securityTitle>
			<value>Genzyme General NQ stock option (right to buy)</value>
		</securityTitle>
		<conversionOrExercisePrice>
			<value>274.32</value>
		</conversionOrExercisePrice>
		<transactionDate>
			<value>2003-06-30</value>
		</transactionDate>
		<transactionCoding>
			<transactionFormType>4</transactionFormType>
			<transactionCode>J</transactionCode>
			<equitySwapInvolved>0</equitySwapInvolved>
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		<transactionAmounts>
			<transactionShares>
				<value>252</value>
				<footnoteId id="F1"/>
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			<transactionValue>
				<value>0</value>
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			<transactionAcquiredDisposedCode>
				<value>A</value>
			</transactionAcquiredDisposedCode>
		</transactionAmounts>
		<exerciseDate>
			<value>2001-05-31</value>
			<footnoteId id="F2"/>
		</exerciseDate>
		<expirationDate>
			<value>2011-05-31</value>
		</expirationDate>
		<underlyingSecurity>
			<underlyingSecurityTitle>
				<value>Genzyme General common stock (GENZ)</value>
			</underlyingSecurityTitle>
			<underlyingSecurityShares>
				<value>252</value>
			</underlyingSecurityShares>
		</underlyingSecurity>
		<postTransactionAmounts>
			<sharesOwnedFollowingTransaction>
				<value>252</value>
			</sharesOwnedFollowingTransaction>
		</postTransactionAmounts>
		<ownershipNature>
			<directOrIndirectOwnership>
				<value>I</value>
			</directOrIndirectOwnership>
			<natureOfOwnership>
				<value>By Spouse</value>
			</natureOfOwnership>
		</ownershipNature>
	</derivativeSecurity>
	<derivativeSecurity>
		<securityTitle>
			<value>Genzyme General NQ stock option (right to buy)</value>
		</securityTitle>
		<conversionOrExercisePrice>
			<value>41.51</value>
		</conversionOrExercisePrice>
		<transactionDate>
			<value>2003-06-30</value>
		</transactionDate>
		<transactionCoding>
			<transactionFormType>4</transactionFormType>
			<transactionCode>J</transactionCode>
			<equitySwapInvolved>0</equitySwapInvolved>
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		<transactionAmounts>
			<transactionShares>
				<value>241</value>
				<footnoteId id="F1"/>
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			<transactionValue>
				<value>0</value>
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			<transactionAcquiredDisposedCode>
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		<exerciseDate>
			<value>2002-05-30</value>
			<footnoteId id="F2"/>
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		<expirationDate>
			<value>2012-05-30</value>
		</expirationDate>
		<underlyingSecurity>
			<underlyingSecurityTitle>
				<value>Genzyme General common stock (GENZ)</value>
			</underlyingSecurityTitle>
			<underlyingSecurityShares>
				<value>241</value>
			</underlyingSecurityShares>
		</underlyingSecurity>
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			<sharesOwnedFollowingTransaction>
				<value>241</value>
			</sharesOwnedFollowingTransaction>
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		<ownershipNature>
			<directOrIndirectOwnership>
				<value>I</value>
			</directOrIndirectOwnership>
			<natureOfOwnership>
				<value>By Spouse</value>
			</natureOfOwnership>
		</ownershipNature>
	</derivativeSecurity>
	<derivativeSecurity>
		<securityTitle>
			<value>Molecular Oncology NQ stock option (right to buy)</value>
		</securityTitle>
		<conversionOrExercisePrice>
			<value>15.40</value>
		</conversionOrExercisePrice>
		<transactionDate>
			<value>2003-06-30</value>
		</transactionDate>
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			<transactionFormType>4</transactionFormType>
			<transactionCode>J</transactionCode>
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		<transactionAmounts>
			<transactionShares>
				<value>4500</value>
				<footnoteId id="F1"/>
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			<transactionValue>
				<value>0</value>
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			<transactionAcquiredDisposedCode>
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		<exerciseDate>
			<value>2001-05-31</value>
			<footnoteId id="F2"/>
		</exerciseDate>
		<expirationDate>
			<value>2011-05-31</value>
		</expirationDate>
		<underlyingSecurity>
			<underlyingSecurityTitle>
				<value>Genzyme Molecular Oncology common stock (GZMO)</value>
			</underlyingSecurityTitle>
			<underlyingSecurityShares>
				<value>4500</value>
			</underlyingSecurityShares>
		</underlyingSecurity>
		<postTransactionAmounts>
			<sharesOwnedFollowingTransaction>
				<value>0</value>
			</sharesOwnedFollowingTransaction>
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		<ownershipNature>
			<directOrIndirectOwnership>
				<value>I</value>
			</directOrIndirectOwnership>
			<natureOfOwnership>
				<value>By Spouse</value>
			</natureOfOwnership>
		</ownershipNature>
	</derivativeSecurity>
	<derivativeSecurity>
		<securityTitle>
			<value>Molecular Oncology NQ stock option (right to buy)</value>
		</securityTitle>
		<conversionOrExercisePrice>
			<value>2.33</value>
		</conversionOrExercisePrice>
		<transactionDate>
			<value>2003-06-30</value>
		</transactionDate>
		<transactionCoding>
			<transactionFormType>4</transactionFormType>
			<transactionCode>J</transactionCode>
			<equitySwapInvolved>0</equitySwapInvolved>
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		<transactionAmounts>
			<transactionShares>
				<value>4300</value>
				<footnoteId id="F1"/>
			</transactionShares>
			<transactionValue>
				<value>0</value>
			</transactionValue>
			<transactionAcquiredDisposedCode>
				<value>D</value>
			</transactionAcquiredDisposedCode>
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		<exerciseDate>
			<value>2002-05-30</value>
			<footnoteId id="F2"/>
		</exerciseDate>
		<expirationDate>
			<value>2012-05-30</value>
		</expirationDate>
		<underlyingSecurity>
			<underlyingSecurityTitle>
				<value>Genzyme Molecular Oncology common stock (GZMO)</value>
			</underlyingSecurityTitle>
			<underlyingSecurityShares>
				<value>4300</value>
			</underlyingSecurityShares>
		</underlyingSecurity>
		<postTransactionAmounts>
			<sharesOwnedFollowingTransaction>
				<value>0</value>
			</sharesOwnedFollowingTransaction>
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		<ownershipNature>
			<directOrIndirectOwnership>
				<value>I</value>
			</directOrIndirectOwnership>
			<natureOfOwnership>
				<value>By Spouse</value>
			</natureOfOwnership>
		</ownershipNature>
	</derivativeSecurity>
	<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>
	</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
0001021040
VAN HEEK G JAN
0
1
0
0
Executive Vice President
Genzyme General NQ stock option (right to buy)
274.32
2003-06-30
4
J
0
252
0
A
2001-05-31
2011-05-31
Genzyme General common stock (GENZ)
252
252
I
By Spouse
Genzyme General NQ stock option (right to buy)
41.51
2003-06-30
4
J
0
241
0
A
2002-05-30
2012-05-30
Genzyme General common stock (GENZ)
241
241
I
By Spouse
Molecular Oncology NQ stock option (right to buy)
15.40
2003-06-30
4
J
0
4500
0
D
2001-05-31
2011-05-31
Genzyme Molecular Oncology common stock (GZMO)
4500
0
I
By Spouse
Molecular Oncology NQ stock option (right to buy)
2.33
2003-06-30
4
J
0
4300
0
D
2002-05-30
2012-05-30
Genzyme Molecular Oncology common stock (GZMO)
4300
0
I
By Spouse
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.
By: Susan P. Cogswell, Attorney-in-Fact
2003-07-02