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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): MAY 16, 2005

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

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

                          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 1.01  ENTRY INTO A MATERIAL DEFINITIVE AGREEMENT

         On May 16, 2005, we entered into a Collaboration and License Agreement
(the "Collaboration Agreement") with N.V. Organon for the joint discovery,
development and commercialization of novel biotherapeutics. In the
collaboration, we will create and analyze mouse knockouts for up to 300 genes
selected by the parties that encode secreted proteins or potential antibody
targets, including two of our existing drug discovery programs. The parties will
jointly select targets for further research and development and will equally
share costs and responsibility for research, preclinical and clinical
activities. The parties will jointly determine the manner in which collaboration
products will be commercialized and will equally benefit from product revenue.
If fewer than five development candidates are designated under the
collaboration, our share of costs and product revenue will be proportionally
reduced. We will receive a milestone payment for each development candidate in
excess of five. Either party may decline to participate in further research or
development efforts with respect to a collaboration product, in which case such
party will receive royalty payments on sales of such collaboration product
rather than sharing in revenue. Organon will have principal responsibility for
manufacturing biotherapeutic products resulting from the collaboration for use
in clinical trials and for worldwide sales.

         We will receive an upfront payment of $22.5 million from Organon in
exchange for access to our drug target discovery capabilities and the exclusive
right to co-develop biotherapeutic products that modulate the 300 genes selected
for the collaboration. Organon will also provide us with annual research funding
totaling up to $50 million for its 50% share of the collaboration's costs during
the four-year target function discovery portion of the alliance.

         Intervet Inc., an affiliate of Organon, is also a party to the
Collaboration Agreement with respect to the development and commercialization of
products in the veterinary field.

                                   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: May 17, 2005                         By: /s/ JEFFREY L. WADE
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                                               Jeffrey L. Wade
                                               Executive Vice President and
                                               General Counsel