-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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<SEC-DOCUMENT>0000732485-06-000004.txt : 20060119
<SEC-HEADER>0000732485-06-000004.hdr.sgml : 20060119
<ACCEPTANCE-DATETIME>20060119130909
ACCESSION NUMBER:		0000732485-06-000004
CONFORMED SUBMISSION TYPE:	4/A
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20060104
FILED AS OF DATE:		20060119
DATE AS OF CHANGE:		20060119

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:			MOSCICKI RICHARD A
		CENTRAL INDEX KEY:			0001021029
		STANDARD INDUSTRIAL CLASSIFICATION:	BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			1231

	FILING VALUES:
		FORM TYPE:		4/A
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14680
		FILM NUMBER:		06537480

	BUSINESS ADDRESS:	
		STREET 1:		C/O GENZYME CORP
		STREET 2:		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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4/A
<SEQUENCE>1
<FILENAME>mos242.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0202</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2006-01-04</periodOfReport>

    <dateOfOriginalSubmission>2006-01-05</dateOfOriginalSubmission>

    <notSubjectToSection16>0</notSubjectToSection16>

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

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001021029</rptOwnerCik>
            <rptOwnerName>MOSCICKI RICHARD A</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>Senior Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Genzyme common stock (GENZ)</value>
            </securityTitle>
            <transactionDate>
                <value>2006-01-04</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>21344</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>15.13</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>26672</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
        <nonDerivativeHolding>
            <securityTitle>
                <value>Genzyme common stock (GENZ)</value>
            </securityTitle>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>218</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>By 401(k)</value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeHolding>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Genzyme ISO stock option (right to buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>15.13</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2006-01-04</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>21344</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>1997-05-17</value>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2006-05-16</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Genzyme common stock (GENZ)</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>21344</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The exercise of this stock option included a distribution of an additional 5 shares of Genzyme common stock.  These stock options were entitled to receive a distribution of shares of Tissue Repair common stock that was paid on July 22, 1997 to Genzyme stockholders at a rate of 0.015.  In connection with the formation of Genzyme Biosurgery in December 2000, shares of Genzyme Tissue Repair were converted into shares of Genzyme Biosurgery at a rate of 0.3352.  In connection with the exchange of Genzyme Biosurgery stock into Genzyme stock on June 30, 2003, distributions of the Genzyme Biosurgery stock are exchanged into Genzyme stock at a rate of 0.04945.</footnote>
        <footnote id="F2">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>2006-01-19</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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