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Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
 NWFcmdgS94/xR4tvdrHQ555r0jJcH6fZXZQbByP3EEowoJOpuFmTvV14KLQulaso
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<SEC-DOCUMENT>0001062822-03-000002.txt : 20030714
<SEC-HEADER>0001062822-03-000002.hdr.sgml : 20030714
<ACCEPTANCE-DATETIME>20030714164222
ACCESSION NUMBER:		0001062822-03-000002
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030710
FILED AS OF DATE:		20030714

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			LEXICON GENETICS INC/TX
		CENTRAL INDEX KEY:			0001062822
		STANDARD INDUSTRIAL CLASSIFICATION:	IN VITRO & IN VIVO DIAGNOSTIC SUBSTANCES [2835]
		IRS NUMBER:				760474169
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		8800 TECHNOLOGY FOREST PLACE
		CITY:			THE WOODLANDS
		STATE:			TX
		ZIP:			77381
		BUSINESS PHONE:		2818633000

	MAIL ADDRESS:	
		STREET 1:		8800 TECHNOLOGY FOREST PLACE
		CITY:			THE WOODLANDS
		STATE:			TX
		ZIP:			77381

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			CASKEY C THOMAS
		CENTRAL INDEX KEY:			0001226858

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-30111
		FILM NUMBER:		03785648

	BUSINESS ADDRESS:	
		STREET 1:		4400 POST OAK PARKWAY
		STREET 2:		SUITE 1400
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77027
		BUSINESS PHONE:		7133367858

	MAIL ADDRESS:	
		STREET 1:		4400 POST OAK PARKWAY
		STREET 2:		SUITE 1400
		CITY:			HOUSTON
		STATE:			TX
		ZIP:			77027
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>cas175.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType>
	<periodOfReport>2003-07-10</periodOfReport>
	<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0001062822</issuerCik>
        <issuerName>LEXICON GENETICS INC/TX</issuerName>
        <issuerTradingSymbol>LEXG</issuerTradingSymbol>
	</issuer>
	<reportingOwner>
		<reportingOwnerId>
            <rptOwnerCik>0001226858</rptOwnerCik>
            <rptOwnerName>CASKEY C THOMAS</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
			<isDirector>1</isDirector>
			<isOfficer>1</isOfficer>
			<isTenPercentOwner>0</isTenPercentOwner>
			<isOther>0</isOther>
			<officerTitle>Chairman of the Board</officerTitle>
		</reportingOwnerRelationship>
	</reportingOwner>
	<nonDerivativeSecurity>
		<securityTitle>
			<value>Common Stock</value>
		</securityTitle>
		<transactionDate>
			<value>2003-07-10</value>
		</transactionDate>
		<transactionCoding>
			<transactionFormType>4</transactionFormType>
			<transactionCode>P</transactionCode>
			<equitySwapInvolved>0</equitySwapInvolved>
		</transactionCoding>
		<transactionAmounts>
			<transactionShares>
				<value>1000000</value>
			</transactionShares>
			<transactionValue>
				<value>4.75</value>
			</transactionValue>
			<transactionAcquiredDisposedCode>
				<value>A</value>
			</transactionAcquiredDisposedCode>
		</transactionAmounts>
		<postTransactionAmounts>
			<sharesOwnedFollowingTransaction>
				<value>1679400.00</value>
			</sharesOwnedFollowingTransaction>
		</postTransactionAmounts>
		<ownershipNature>
			<directOrIndirectOwnership>
				<value>I</value>
			</directOrIndirectOwnership>
			<natureOfOwnership>
				<value>By Cogene Biotech Ventures, L.P.</value>
				<footnoteId id="F1"/>
			</natureOfOwnership>
		</ownershipNature>
	</nonDerivativeSecurity>
	<footnotes>
		<footnote id="F1">Represents shares held by Cogene Biotech Ventures, L.P., of which Dr. Caskey is President and CEO.  Dr. Caskey disclaims beneficial ownership of such shares except to the extent of his pecuniary interest therein.</footnote>
	</footnotes>
	<ownerSignature>
		<signatureName>/s/ Caskey, C. Thomas</signatureName>
		<signatureDate>2003-07-11</signatureDate>
	</ownerSignature>
</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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