<SUBMISSION>
<ACCESSION-NUMBER>0001209191-03-012483
<TYPE>3
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20030710
<FILING-DATE>20030718
<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>MCNAIR ROBERT C
<CIK>0001080723
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>3
<ACT>34
<FILE-NUMBER>000-30111
<FILM-NUMBER>03793276
</FILING-VALUES>
<BUSINESS-ADDRESS>
<STREET1>711 LOUISIANA STREET 33RD FLOOR
<CITY>HOUSTON
<STATE>TX
<ZIP>77002
<PHONE>7133367700
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>711 LOUISIANA STREET 33RD FLOOR
<CITY>HOUSTON
<STATE>TX
<ZIP>77002
</MAIL-ADDRESS>
</REPORTING-OWNER>
<DOCUMENT>
<TYPE>3
<SEQUENCE>1
<FILENAME>boh07527_boh1rcm.xml
<DESCRIPTION>MAIN DOCUMENT DESCRIPTION
<TEXT>
<XML>
<?xml version="1.0"?><ownershipDocument><schemaVersion>X0101</schemaVersion>    <documentType>3</documentType><periodOfReport>2003-07-10</periodOfReport><noSecuritiesOwned>0</noSecuritiesOwned><issuer><issuerCik>0001062822</issuerCik><issuerName>LEXICON GENETICS INC/TX</issuerName>        <issuerTradingSymbol>LEXG</issuerTradingSymbol></issuer><reportingOwner><reportingOwnerId><rptOwnerCik>0001080723</rptOwnerCik><rptOwnerName>MCNAIR ROBERT C</rptOwnerName></reportingOwnerId><reportingOwnerAddress><rptOwnerStreet1>  </rptOwnerStreet1><rptOwnerStreet2>  </rptOwnerStreet2><rptOwnerCity>  </rptOwnerCity><rptOwnerState>  </rptOwnerState><rptOwnerZipCode>  </rptOwnerZipCode></reportingOwnerAddress><reportingOwnerRelationship><isDirector>0</isDirector><isOfficer>0</isOfficer><isTenPercentOwner>1</isTenPercentOwner><isOther>0</isOther></reportingOwnerRelationship></reportingOwner><nonDerivativeSecurity><securityTitle><value>Common stock, par value $0.001 per share</value></securityTitle><transactionAmounts><transactionShares><value>4250000</value></transactionShares></transactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By RCM Financial Services, L.P.</value><footnoteId id="F1" /></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common stock, par value $0.001 per share</value></securityTitle><transactionAmounts><transactionShares><value>20000</value></transactionShares></transactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By Palmetto Partners, Ltd.</value><footnoteId id="F2" /></natureOfOwnership></ownershipNature></nonDerivativeSecurity><nonDerivativeSecurity><securityTitle><value>Common stock, par value $0.001 per share</value></securityTitle><transactionAmounts><transactionShares><value>1679400</value></transactionShares></transactionAmounts><ownershipNature><directOrIndirectOwnership><value>I</value></directOrIndirectOwnership><natureOfOwnership><value>By Cogene Biotech Ventures, L.P.</value><footnoteId id="F3" /></natureOfOwnership></ownershipNature></nonDerivativeSecurity><footnotes><footnote id="F1">The reporting person is the sole limited partner of RCM Financial Services, L.P., and the sole director and stockholder of RCM Financial Services GP, Inc., which serves as the sole general partner of RCM Financial Services, L.P.</footnote><footnote id="F2">The reporting person is the sole limited partner of Palmetto Partners, Ltd., and the sole director and stockholder of Palmetto Capital Corporation, which serves as the sole general partner of Palmetto Partners, Ltd.</footnote><footnote id="F3">Palmetto Partners, Ltd. owns a 74% limited partner interest in Cogene Biotech Ventures, L.P.  Palmetto Partners, Ltd. is the sole member of Cogene Biotech Ventures GP, L.L.C., which serves as the sole general partner of Cogene Biotech Ventures, L.P. The reporting person disclaims beneficial ownership of the securities held by Cogene Biotech Ventures, L.P., except to the extent of his pecuniary interest therein.</footnote></footnotes><ownerSignature><signatureName> Robert C. McNair</signatureName><signatureDate>2003-07-18</signatureDate></ownerSignature></ownershipDocument>

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