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Proc-Type: 2001,MIC-CLEAR
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<SEC-DOCUMENT>0000732485-03-000008.txt : 20030702
<SEC-HEADER>0000732485-03-000008.hdr.sgml : 20030702
<ACCEPTANCE-DATETIME>20030701200330
ACCESSION NUMBER:		0000732485-03-000008
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030630
FILED AS OF DATE:		20030702

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			MCGILLICUDY CORNELIUS III
		CENTRAL INDEX KEY:			0001136998

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-14680
		FILM NUMBER:		03769370

	BUSINESS ADDRESS:	
		STREET 1:		2300 N STREET NW
		CITY:			WASHINGTON
		STATE:			DC
		ZIP:			20037

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
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
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				<value>0</value>
			</transactionValue>
			<transactionAcquiredDisposedCode>
				<value>D</value>
			</transactionAcquiredDisposedCode>
		</transactionAmounts>
		<exerciseDate>
			<value>2001-05-31</value>
			<footnoteId id="F2"/>
		</exerciseDate>
		<expirationDate>
			<value>2011-02-12</value>
		</expirationDate>
		<underlyingSecurity>
			<underlyingSecurityTitle>
				<value>Genzyme Molecular Oncology common stock (GZMO)</value>
			</underlyingSecurityTitle>
			<underlyingSecurityShares>
				<value>12000</value>
			</underlyingSecurityShares>
		</underlyingSecurity>
		<postTransactionAmounts>
			<sharesOwnedFollowingTransaction>
				<value>0</value>
			</sharesOwnedFollowingTransaction>
		</postTransactionAmounts>
		<ownershipNature>
			<directOrIndirectOwnership>
				<value>D</value>
			</directOrIndirectOwnership>
			<natureOfOwnership>
				<value/>
			</natureOfOwnership>
		</ownershipNature>
	</derivativeSecurity>
	<derivativeSecurity>
		<securityTitle>
			<value>Molecular Oncology DOP stock option (right to buy)</value>
		</securityTitle>
		<conversionOrExercisePrice>
			<value>15.40</value>
		</conversionOrExercisePrice>
		<transactionDate>
			<value>2003-06-30</value>
		</transactionDate>
		<transactionCoding>
			<transactionFormType>4</transactionFormType>
			<transactionCode>J</transactionCode>
			<equitySwapInvolved>0</equitySwapInvolved>
		</transactionCoding>
		<transactionAmounts>
			<transactionShares>
				<value>4000</value>
				<footnoteId id="F1"/>
			</transactionShares>
			<transactionValue>
				<value>0</value>
			</transactionValue>
			<transactionAcquiredDisposedCode>
				<value>D</value>
			</transactionAcquiredDisposedCode>
		</transactionAmounts>
		<exerciseDate>
			<value>2002-05-31</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>4000</value>
			</underlyingSecurityShares>
		</underlyingSecurity>
		<postTransactionAmounts>
			<sharesOwnedFollowingTransaction>
				<value>0</value>
			</sharesOwnedFollowingTransaction>
		</postTransactionAmounts>
		<ownershipNature>
			<directOrIndirectOwnership>
				<value>D</value>
			</directOrIndirectOwnership>
			<natureOfOwnership>
				<value/>
			</natureOfOwnership>
		</ownershipNature>
	</derivativeSecurity>
	<derivativeSecurity>
		<securityTitle>
			<value>Molecular Oncology DOP Stock Option (right to buy)</value>
		</securityTitle>
		<conversionOrExercisePrice>
			<value>2.58</value>
		</conversionOrExercisePrice>
		<transactionDate>
			<value>2003-06-30</value>
		</transactionDate>
		<transactionCoding>
			<transactionFormType>4</transactionFormType>
			<transactionCode>J</transactionCode>
			<equitySwapInvolved>0</equitySwapInvolved>
		</transactionCoding>
		<transactionAmounts>
			<transactionShares>
				<value>18000</value>
				<footnoteId id="F1"/>
			</transactionShares>
			<transactionValue>
				<value>0</value>
			</transactionValue>
			<transactionAcquiredDisposedCode>
				<value>D</value>
			</transactionAcquiredDisposedCode>
		</transactionAmounts>
		<exerciseDate>
			<value>2004-05-29</value>
			<footnoteId id="F2"/>
		</exerciseDate>
		<expirationDate>
			<value>2013-05-29</value>
		</expirationDate>
		<underlyingSecurity>
			<underlyingSecurityTitle>
				<value>Genzyme Molecular Oncology common stock (GZMO)</value>
			</underlyingSecurityTitle>
			<underlyingSecurityShares>
				<value>18000</value>
			</underlyingSecurityShares>
		</underlyingSecurity>
		<postTransactionAmounts>
			<sharesOwnedFollowingTransaction>
				<value>0</value>
			</sharesOwnedFollowingTransaction>
		</postTransactionAmounts>
		<ownershipNature>
			<directOrIndirectOwnership>
				<value>D</value>
			</directOrIndirectOwnership>
			<natureOfOwnership>
				<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 1/3 annual increments on the dates of the next three annual meetings of shareholders following the original date of grant.</footnote>
		<footnote id="F3">Options vest in 50% increments on May 31, 2002 and May 31, 2003.</footnote>
	</footnotes>
	<ownerSignature>
		<signatureName>By: Susan P. Cogswell, Attorney-in-Fact</signatureName>
		<signatureDate>2003-07-01</signatureDate>
	</ownerSignature>
</ownershipDocument>

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</TEXT>
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