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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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                                    FORM 8-K

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                                 CURRENT REPORT
     PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934


         DATE OF REPORT (DATE OF EARLIEST EVENT REPORTED): JULY 28, 2005


                          LEXICON GENETICS INCORPORATED
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)


<Table>
<Caption>
                                                                                
                DELAWARE                              000-30111                             76-0474169
    (STATE OR OTHER JURISDICTION OF            (COMMISSION FILE NUMBER)                  (I.R.S. EMPLOYER
     INCORPORATION OR ORGANIZATION)                                                   IDENTIFICATION NUMBER)
</Table>


                          8800 TECHNOLOGY FOREST PLACE
                           THE WOODLANDS, TEXAS 77381
                         (ADDRESS OF PRINCIPAL EXECUTIVE
                              OFFICES AND ZIP CODE)


                                 (281) 863-3000
                         (REGISTRANT'S TELEPHONE NUMBER,
                              INCLUDING AREA CODE)


      Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligations of the registrant under any of the
following provisions:

[ ]     Written communications pursuant to Rule 425 under the Securities Act
        (17 CFR 230.425)

[ ]     Soliciting material pursuant to Rule 14a-12 under the Exchange Act
        (17 CFR 240.14a-12)

[ ]     Pre-commencement communications pursuant to Rule 14d-2(b) under the
        Exchange Act (17 CFR 240.14d-2(b))

[ ]     Pre-commencement communications pursuant to Rule 13e-4(c) under the
        Exchange Act (17 CFR 240.13e-4(c))


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ITEM 2.02     RESULTS OF OPERATIONS AND FINANCIAL CONDITION

         On July 28, 2005, we issued a press release to report our financial
results for the quarter ended June 30, 2005. A copy of the press release is
attached to this current report on Form 8-K as Exhibit 99.1.

         The information in this Form 8-K and the Exhibit attached to this Form
8-K shall not be deemed "filed" for purposes of Section 18 of the Securities
Exchange Act of 1934 (the "Exchange Act") or otherwise subject to the
liabilities of that section, nor shall it be deemed incorporated by reference in
any filing under the Securities Act of 1933 or the Exchange Act, except as
expressly set forth by specific reference in such a filing.


ITEM 9.01     FINANCIAL STATEMENTS AND EXHIBITS

      (c)     Exhibits


EXHIBIT NO.                            DESCRIPTION
- -----------                            -----------
  99.1        --     Press Release of Lexicon Genetics Incorporated dated
                     July 28, 2005



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                                   SIGNATURES

         Pursuant to the requirements of the Securities Exchange Act of 1934,
the registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.



                                               LEXICON GENETICS INCORPORATED


Date:   July 28, 2005                          By:  /s/ JEFFREY L. WADE
                                                    ----------------------------
                                                    Jeffrey L. Wade
                                                    Executive Vice President and
                                                    General Counsel


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                                INDEX TO EXHIBITS



EXHIBIT NO.                                 DESCRIPTION
- -----------                                 -----------
   99.1           --    Press Release of Lexicon Genetics Incorporated dated
                        July 28, 2005