<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>
	<periodOfReport>2003-09-03</periodOfReport>
	<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000732485</issuerCik>
        <issuerName>GENZYME CORP</issuerName>
        <issuerTradingSymbol>GENZ</issuerTradingSymbol>
	</issuer>
	<reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001021037</rptOwnerCik>
            <rptOwnerName>SMITH ALAN E</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>GENZYME CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>ONE KENDALL SQUARE</rptOwnerStreet2>
            <rptOwnerCity>CAMBRIDGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>021391562</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
			<isDirector>0</isDirector>
			<isOfficer>1</isOfficer>
			<isTenPercentOwner>0</isTenPercentOwner>
			<isOther>0</isOther>
			<officerTitle>Senior Vice President</officerTitle>
		</reportingOwnerRelationship>
	</reportingOwner>
	<nonDerivativeTable>
		<nonDerivativeTransaction>
			<securityTitle>
				<value>Genzyme General common stock (GENZ)</value>
			</securityTitle>
			<transactionDate>
				<value>2003-09-03</value>
			</transactionDate>
			<deemedExecutionDate>
			</deemedExecutionDate>
			<transactionCoding>
				<transactionFormType>4</transactionFormType>
				<transactionCode>M</transactionCode>
				<equitySwapInvolved>0</equitySwapInvolved>
			</transactionCoding>
			<transactionAmounts>
				<transactionShares>
					<value>4818</value>
				</transactionShares>
				<transactionPricePerShare>
					<value>20.75</value>
				</transactionPricePerShare>
				<transactionAcquiredDisposedCode>
					<value>A</value>
				</transactionAcquiredDisposedCode>
			</transactionAmounts>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>63723</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>D</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value/>
				</natureOfOwnership>
			</ownershipNature>
		</nonDerivativeTransaction>
		<nonDerivativeTransaction>
			<securityTitle>
				<value>Genzyme General common stock (GENZ)</value>
			</securityTitle>
			<transactionDate>
				<value>2003-09-03</value>
			</transactionDate>
			<deemedExecutionDate>
			</deemedExecutionDate>
			<transactionCoding>
				<transactionFormType>4</transactionFormType>
				<transactionCode>M</transactionCode>
				<equitySwapInvolved>0</equitySwapInvolved>
			</transactionCoding>
			<transactionAmounts>
				<transactionShares>
					<value>3075</value>
				</transactionShares>
				<transactionPricePerShare>
					<value>32.52</value>
				</transactionPricePerShare>
				<transactionAcquiredDisposedCode>
					<value>A</value>
				</transactionAcquiredDisposedCode>
			</transactionAmounts>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>66798</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>D</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value/>
				</natureOfOwnership>
			</ownershipNature>
		</nonDerivativeTransaction>
		<nonDerivativeHolding>
			<securityTitle>
				<value>Genzyme General common stock (GENZ)</value>
			</securityTitle>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>221</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>I</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value>By 401(k)</value>
				</natureOfOwnership>
			</ownershipNature>
		</nonDerivativeHolding>
	</nonDerivativeTable>
	<derivativeTable>
		<derivativeTransaction>
			<securityTitle>
				<value>Genzyme General ISO stock option (right to buy)</value>
			</securityTitle>
			<conversionOrExercisePrice>
				<value>20.75</value>
			</conversionOrExercisePrice>
			<transactionDate>
				<value>2003-09-03</value>
			</transactionDate>
			<deemedExecutionDate>
			</deemedExecutionDate>
			<transactionCoding>
				<transactionFormType>4</transactionFormType>
				<transactionCode>M</transactionCode>
				<equitySwapInvolved>0</equitySwapInvolved>
			</transactionCoding>
			<transactionAmounts>
				<transactionShares>
					<value>4818</value>
				</transactionShares>
				<transactionPricePerShare>
					<value>0</value>
				</transactionPricePerShare>
				<transactionAcquiredDisposedCode>
					<value>D</value>
				</transactionAcquiredDisposedCode>
			</transactionAmounts>
			<exerciseDate>
				<value>1998-12-01</value>
				<footnoteId id="F1"/>
			</exerciseDate>
			<expirationDate>
				<value>2008-12-01</value>
			</expirationDate>
			<underlyingSecurity>
				<underlyingSecurityTitle>
					<value>Genzyme General common stock (GENZ)</value>
				</underlyingSecurityTitle>
				<underlyingSecurityShares>
					<value>4818</value>
				</underlyingSecurityShares>
			</underlyingSecurity>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>0</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>D</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value/>
				</natureOfOwnership>
			</ownershipNature>
		</derivativeTransaction>
		<derivativeTransaction>
			<securityTitle>
				<value>Genzyme General ISO stock option (right to buy)</value>
			</securityTitle>
			<conversionOrExercisePrice>
				<value>32.52</value>
			</conversionOrExercisePrice>
			<transactionDate>
				<value>2003-09-03</value>
			</transactionDate>
			<deemedExecutionDate>
			</deemedExecutionDate>
			<transactionCoding>
				<transactionFormType>4</transactionFormType>
				<transactionCode>M</transactionCode>
				<equitySwapInvolved>0</equitySwapInvolved>
			</transactionCoding>
			<transactionAmounts>
				<transactionShares>
					<value>3075</value>
				</transactionShares>
				<transactionPricePerShare>
					<value>0</value>
				</transactionPricePerShare>
				<transactionAcquiredDisposedCode>
					<value>D</value>
				</transactionAcquiredDisposedCode>
			</transactionAmounts>
			<exerciseDate>
				<value>2003-05-30</value>
				<footnoteId id="F1"/>
			</exerciseDate>
			<expirationDate>
				<value>2012-05-30</value>
			</expirationDate>
			<underlyingSecurity>
				<underlyingSecurityTitle>
					<value>Genzyme General common stock (GENZ)</value>
				</underlyingSecurityTitle>
				<underlyingSecurityShares>
					<value>3075</value>
				</underlyingSecurityShares>
			</underlyingSecurity>
			<postTransactionAmounts>
				<sharesOwnedFollowingTransaction>
					<value>9225</value>
				</sharesOwnedFollowingTransaction>
			</postTransactionAmounts>
			<ownershipNature>
				<directOrIndirectOwnership>
					<value>D</value>
				</directOrIndirectOwnership>
				<natureOfOwnership>
					<value/>
				</natureOfOwnership>
			</ownershipNature>
		</derivativeTransaction>
	</derivativeTable>
	<footnotes>
		<footnote id="F1">Options vest in 20% annual increments beginning on the original date of grant.</footnote>
	</footnotes>
	<remarks>
	</remarks>
	<ownerSignature>
		<signatureName>By: Susan P. Cogswell, Attorney-in-Fact</signatureName>
		<signatureDate>2003-09-04</signatureDate>
	</ownerSignature>
</ownershipDocument>
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X0201
4
2003-09-03
0
0000732485
GENZYME CORP
GENZ
0001021037
SMITH ALAN E
GENZYME CORPORATION
ONE KENDALL SQUARE
CAMBRIDGE
MA
021391562
0
1
0
0
Senior Vice President
Genzyme General common stock (GENZ)
2003-09-03
4
M
0
4818
20.75
A
63723
D
Genzyme General common stock (GENZ)
2003-09-03
4
M
0
3075
32.52
A
66798
D
Genzyme General common stock (GENZ)
221
I
By 401(k)
Genzyme General ISO stock option (right to buy)
20.75
2003-09-03
4
M
0
4818
0
D
1998-12-01
2008-12-01
Genzyme General common stock (GENZ)
4818
0
D
Genzyme General ISO stock option (right to buy)
32.52
2003-09-03
4
M
0
3075
0
D
2003-05-30
2012-05-30
Genzyme General common stock (GENZ)
3075
9225
D
Options vest in 20% annual increments beginning on the original date of grant.
By: Susan P. Cogswell, Attorney-in-Fact
2003-09-04