<SUBMISSION>
<ACCESSION-NUMBER>0001062822-03-000002
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20030710
<FILING-DATE>20030714
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>LEXICON GENETICS INC/TX
<CIK>0001062822
<ASSIGNED-SIC>2835
<IRS-NUMBER>760474169
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>8800 TECHNOLOGY FOREST PLACE
<CITY>THE WOODLANDS
<STATE>TX
<ZIP>77381
<PHONE>2818633000
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>8800 TECHNOLOGY FOREST PLACE
<CITY>THE WOODLANDS
<STATE>TX
<ZIP>77381
</MAIL-ADDRESS>
</ISSUER>
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>CASKEY C THOMAS
<CIK>0001226858
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-30111
<FILM-NUMBER>03785648
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>4400 POST OAK PARKWAY
<STREET2>SUITE 1400
<CITY>HOUSTON
<STATE>TX
<ZIP>77027
<PHONE>7133367858
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>4400 POST OAK PARKWAY
<STREET2>SUITE 1400
<CITY>HOUSTON
<STATE>TX
<ZIP>77027
</MAIL-ADDRESS>
</REPORTING-OWNER>
<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>
</SUBMISSION>
