-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0000732485-07-000003.txt : 20070207
<SEC-HEADER>0000732485-07-000003.hdr.sgml : 20070207
<ACCEPTANCE-DATETIME>20070207133346
ACCESSION NUMBER:		0000732485-07-000003
CONFORMED SUBMISSION TYPE:	3/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20050526
FILED AS OF DATE:		20070207
DATE AS OF CHANGE:		20070207

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			GENZYME CORP
		CENTRAL INDEX KEY:			0000732485
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		IRS NUMBER:				061047163
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		ONE KENDALL SQ
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139
		BUSINESS PHONE:		6172527500

	MAIL ADDRESS:	
		STREET 1:		ONE KENDALL SQUARE
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			SMITH SANDFORD D
		CENTRAL INDEX KEY:			0001243004

	FILING VALUES:
		FORM TYPE:		3/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14680
		FILM NUMBER:		07587231

	MAIL ADDRESS:	
		STREET 1:		C/O ARIAD PHARMACEUTICALS INC
		STREET 2:		26 LANDSDOWNE STREET
		CITY:			CAMBRIDGE
		STATE:			MA
		ZIP:			02139
</SEC-HEADER>
<DOCUMENT>
<TYPE>3/A
<SEQUENCE>1
<FILENAME>smi303.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>3/A</documentType>

    <periodOfReport>2005-05-26</periodOfReport>

    <dateOfOriginalSubmission>2005-06-08</dateOfOriginalSubmission>

    <noSecuritiesOwned>0</noSecuritiesOwned>

    <issuer>
        <issuerCik>0000732485</issuerCik>
        <issuerName>GENZYME CORP</issuerName>
        <issuerTradingSymbol>GENZ</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001243004</rptOwnerCik>
            <rptOwnerName>SMITH SANDFORD D</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>GENZYME CORPORATION</rptOwnerStreet1>
            <rptOwnerStreet2>500 KENDALL STREET</rptOwnerStreet2>
            <rptOwnerCity>CAMBRIDGE</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02142</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Executive Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Genzyme common stock (GENZ)</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1811</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Genzyme common stock (GENZ)</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>1118</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By 401(k)</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme ISO stock option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>837.07</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>1997-04-15</value>
                <footnoteId id="F1"/>
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            <expirationDate>
                <value>2006-04-15</value>
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                <underlyingSecurityTitle>
                    <value>Genzyme common stock (GENZ)</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>41</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme ISO stock option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>124.69</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-05-28</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2008-05-28</value>
            </expirationDate>
            <underlyingSecurity>
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                    <value>Genzyme common stock (GENZ)</value>
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                <underlyingSecurityShares>
                    <value>66</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
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                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme ISO stock option (right to buy)</value>
            </securityTitle>
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                <value>392.13</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2001-05-28</value>
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            <expirationDate>
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            <ownershipNature>
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            <securityTitle>
                <value>Genzyme ISO stock option (right to buy)</value>
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            <exerciseDate>
                <value>2005-05-30</value>
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            <expirationDate>
                <value>2012-05-30</value>
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            <underlyingSecurity>
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            </underlyingSecurity>
            <ownershipNature>
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                    <value>D</value>
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                <natureOfOwnership>
                    <value></value>
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            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme NQ stock option (right to buy)</value>
            </securityTitle>
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                <value>135.25</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2000-05-25</value>
                <footnoteId id="F4"/>
            </exerciseDate>
            <expirationDate>
                <value>2011-02-09</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Genzyme common stock (GENZ)</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>351</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
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                    <value></value>
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            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme NQ stock option (right to buy)</value>
            </securityTitle>
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                <value>837.07</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-06-15</value>
            </exerciseDate>
            <expirationDate>
                <value>2005-12-15</value>
            </expirationDate>
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                <underlyingSecurityTitle>
                    <value>Genzyme common stock (GENZ)</value>
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                <underlyingSecurityShares>
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                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
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                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme NQ stock option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>595.75</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>1997-10-16</value>
                <footnoteId id="F5"/>
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            <expirationDate>
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            </underlyingSecurity>
            <ownershipNature>
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        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme NQ stock option (right to buy)</value>
            </securityTitle>
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            <exerciseDate>
                <value>1998-05-28</value>
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            <expirationDate>
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            <ownershipNature>
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        <derivativeHolding>
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        </derivativeHolding>
        <derivativeHolding>
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                <value>2002-05-30</value>
                <footnoteId id="F6"/>
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            <expirationDate>
                <value>2012-05-30</value>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Genzyme common stock (GENZ)</value>
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                </underlyingSecurityShares>
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        </derivativeHolding>
        <derivativeHolding>
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            <exerciseDate>
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            <underlyingSecurity>
                <underlyingSecurityTitle>
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                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme NQ Stock Option (right to buy)</value>
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            <conversionOrExercisePrice>
                <value>46.24</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2003-05-29</value>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2013-05-29</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Genzyme common stock (GENZ)</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>45000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme NQ stock option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>43.90</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2004-05-27</value>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-05-27</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Genzyme common stock (GENZ)</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>57000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Genzyme NQ Stock Option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>62.98</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2005-05-26</value>
                <footnoteId id="F6"/>
            </exerciseDate>
            <expirationDate>
                <value>2015-05-26</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Genzyme common stock (GENZ)</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>48500</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Options vest in 25% annual increments beginning on the one year anniversary of the original date of grant.</footnote>
        <footnote id="F2">Options vest 50% on each of 5/29/01 and 5/28/02.</footnote>
        <footnote id="F3">Options vest 50% on each of 5/29/05 and 5/30/06.</footnote>
        <footnote id="F4">Options vest in 20% annual increments beginning 5/25/2000.</footnote>
        <footnote id="F5">Options vest 20% on October 16, 1997 and in 20% annual increments beginning May 16, 1998.</footnote>
        <footnote id="F6">Options vest in 20% annual increments beginning on the original date of grant.</footnote>
        <footnote id="F7">Options vest in 1/3 increments on each of 5/28/98, 5/28/99 and 5/28/00.</footnote>
        <footnote id="F8">Options were granted with an exercise price 100% above fair market value, and vest in 1/3 increments on each of Janary 25, 2001, 2002 and 2003.</footnote>
        <footnote id="F9">Options vest 20% on August 26, 1999 and in 20% annual increments beginning May 26, 2000.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>By: Susan P. Cogswell, Attorney-in-Fact</signatureName>
        <signatureDate>2007-02-07</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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