================================================================================

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

                                    FORM 10-Q

(MARK ONE)

    [X]    QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
           EXCHANGE ACT OF 1934

           FOR THE QUARTERLY PERIOD ENDED SEPTEMBER 30, 2005

                                       OR

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

           FOR THE TRANSITION PERIOD FROM _____________ TO _____________

                        COMMISSION FILE NUMBER: 000-30111

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

           DELAWARE                                             76-0474169
(STATE OR OTHER JURISDICTION OF                              (I.R.S. EMPLOYER
INCORPORATION OR ORGANIZATION)                            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)

      Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports) and (2) has been subject to such
filing requirements for the past 90 days.

                                  Yes [X] No [ ]

      Indicate by check mark whether the registrant is an accelerated filer (as
defined in Rule 12b-2 of the Exchange Act.

                                 Yes [X] No [ ]

      As of October 27, 2005, 64,537,089 shares of the registrant's common
stock, par value $0.001 per share, were outstanding.

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                          LEXICON GENETICS INCORPORATED

                                TABLE OF CONTENTS



                                                                                                  PAGE
                                                                                                  ----
                                                                                               
FACTORS AFFECTING FORWARD-LOOKING STATEMENTS....................................................    2
PART I - FINANCIAL INFORMATION
Item 1.  Financial Statements
         Consolidated Balance Sheets - September 30, 2005 (unaudited) and December 31, 2004.....    3
         Consolidated Statements of Operations (unaudited) - Three and Nine Months Ended
              September 30, 2005 and 2004.......................................................    4
         Consolidated Statements of Cash Flows (unaudited) - Nine Months Ended
              September 30, 2005 and 2004.......................................................    5
         Notes to Consolidated Financial Statements (unaudited).................................    6
Item 2.  Management's Discussion and Analysis of Financial Condition and
         Results of Operations..................................................................    9
Item 3.  Quantitative and Qualitative Disclosures About Market Risk.............................   19
Item 4.  Controls and Procedures................................................................   19
PART II - OTHER INFORMATION
Item 5.  Other Information......................................................................   20
Item 6.  Exhibits and Reports on Form 8-K.......................................................   20
SIGNATURES......................................................................................   21


      The Lexicon name and logo, LexVision(R) and OmniBank(R) are registered
trademarks and Genome5000(TM) and e-Biology(TM) are trademarks of Lexicon
Genetics Incorporated.

                  FACTORS AFFECTING FORWARD LOOKING STATEMENTS

      This quarterly report on Form 10-Q contains forward-looking statements.
These statements relate to future events or our future financial performance. We
have attempted to identify forward-looking statements by terminology including
"anticipate," "believe," "can," "continue," "could," "estimate," "expect,"
"intend," "may," "plan," "potential," "predict," "should" or "will" or the
negative of these terms or other comparable terminology. These statements are
only predictions and involve known and unknown risks, uncertainties and other
factors, including the risks outlined under "Item 2. Management's Discussion and
Analysis of Financial Condition and Results of Operations - Risk Factors," that
may cause our or our industry's actual results, levels of activity, performance
or achievements to be materially different from any future results, levels or
activity, performance or achievements expressed or implied by these
forward-looking statements.

      Although we believe that the expectations reflected in the forward-looking
statements are reasonable, we cannot guarantee future results, levels of
activity, performance or achievements. We are not under any duty to update any
of the forward-looking statements after the date of this quarterly report on
Form 10-Q to conform these statements to actual results, unless required by law.

                                       2


PART I - FINANCIAL INFORMATION

ITEM 1. FINANCIAL STATEMENTS

                          LEXICON GENETICS INCORPORATED

                           CONSOLIDATED BALANCE SHEETS
                        (IN THOUSANDS, EXCEPT PAR VALUE)



                                                                             AS OF SEPTEMBER 30,      AS OF DECEMBER 31,
                                                                                     2005                   2004
                                                                             -------------------      ------------------
                                   ASSETS                                        (UNAUDITED)
                                                                                                
Current assets:
    Cash and cash equivalents............................................     $         23,120        $          14,612
    Short-term investments, including restricted investments of $430.....               67,121                   72,946
    Accounts receivable, net of allowance for doubtful accounts of $75...                1,698                    5,345
    Other receivables....................................................                    -                    1,052
    Prepaid expenses and other current assets............................                3,433                    4,793
                                                                              ----------------        -----------------
       Total current assets..............................................               95,372                   98,748
Property and equipment, net of accumulated depreciation
    of $45,532 and $41,892, respectively.................................               85,996                   84,573
Goodwill.................................................................               25,798                   25,798
Intangible assets, net of amortization of $5,060 and $4,160,
    respectively.........................................................                  940                    1,840
Other assets.............................................................                  861                    1,021
                                                                              ----------------        -----------------
       Total assets......................................................     $        208,967        $         211,980
                                                                              ================        =================

                    LIABILITIES AND STOCKHOLDERS' EQUITY

Current liabilities:
    Accounts payable.....................................................     $          3,751        $           7,574
    Accrued liabilities..................................................                8,032                    6,945
    Current portion of deferred revenue..................................               31,800                   19,500
    Current portion of long-term debt....................................                4,736                    4,691
                                                                              ----------------        -----------------
       Total current liabilities.........................................               48,319                   38,710
Deferred revenue, net of current portion.................................               47,695                   18,092
Long-term debt...........................................................               32,384                   32,940
Other long-term liabilities..............................................                  715                      644
                                                                              ----------------        -----------------
       Total liabilities.................................................              129,113                   90,386

Commitments and contingencies

Stockholders' equity:
    Preferred stock, $.01 par value; 5,000 shares authorized;
       no shares issued and outstanding..................................                    -                        -
    Common stock, $.001 par value; 120,000 shares authorized;
       64,537 and 63,491 shares issued and outstanding...................                   64                       63
    Additional paid-in capital...........................................              383,193                  382,666
    Deferred stock compensation..........................................                   (5)                     (20)
    Accumulated deficit..................................................             (303,344)                (261,115)
    Accumulated other comprehensive loss.................................                  (54)                      --
                                                                              ----------------        -----------------
       Total stockholders' equity........................................               79,854                  121,594
                                                                              ----------------        -----------------
       Total liabilities and stockholders' equity........................     $        208,967        $         211,980
                                                                              ================        =================


   The accompanying notes are an integral part of these consolidated financial
                                   statements.

                                       3


                          LEXICON GENETICS INCORPORATED

                      CONSOLIDATED STATEMENTS OF OPERATIONS
                    (IN THOUSANDS, EXCEPT PER SHARE AMOUNTS)
                                   (UNAUDITED)



                                                  THREE MONTHS ENDED SEPTEMBER 30,  NINE MONTHS ENDED SEPTEMBER 30,
                                                  ------------------------------    -------------------------------
                                                        2005             2004            2005             2004
                                                  --------------    -------------   --------------   -------------
                                                                                         
Revenues:
   Collaborative research.......................   $      13,520    $      11,492    $      36,174   $      27,997
   Subscription and license fees................             443            1,617            5,612           7,732
                                                   -------------    -------------    -------------   -------------
     Total revenues.............................          13,963           13,109           41,786          35,729
Operating expenses:
   Research and development.....................          23,344           22,485           69,771          67,466
   General and administrative...................           4,674            4,573           13,856          14,259
                                                   -------------    -------------    -------------   -------------
     Total operating expenses...................          28,018           27,058           83,627          81,725
                                                   -------------    -------------    -------------   -------------
Loss from operations............................         (14,055)         (13,949)         (41,841)        (45,996)
Interest income.................................             767              405            1,764           1,198
Interest expense................................            (833)            (833)          (2,465)         (1,829)
Other income, net...............................               -                -              313              (4)
                                                   -------------    -------------    -------------   -------------
Net loss  ......................................   $     (14,121)   $     (14,377)   $     (42,229)  $     (46,631)
                                                   =============    =============    =============   =============
Net loss per common share, basic and diluted....   $       (0.22)   $       (0.23)   $       (0.66)  $       (0.74)
Shares used in computing net loss per
   common share, basic and diluted..............          64,134           63,422           63,767          63,286


   The accompanying notes are an integral part of these consolidated financial
                                   statements.

                                       4


                          LEXICON GENETICS INCORPORATED

                      CONSOLIDATED STATEMENTS OF CASH FLOWS
                                 (IN THOUSANDS)
                                   (UNAUDITED)



                                                                              NINE MONTHS ENDED SEPTEMBER 30,
                                                                            ----------------------------------
                                                                                 2005                2004
                                                                            -------------       -------------
                                                                                          
Cash flows from operating activities:
   Net loss..............................................................   $     (42,229)      $     (46,631)
   Adjustments to reconcile net loss to net cash used in operating
     activities:
     Depreciation........................................................           7,835               7,976
     Amortization of intangible assets, other than goodwill..............             900                 900
     Amortization of deferred stock compensation.........................             (20)                827
     Loss on disposal of property and equipment..........................              10                   -
     Changes in operating assets and liabilities:
       Decrease in accounts receivable...................................           4,699               4,558
       (Increase) decrease in prepaid expenses and other current assets..           1,360                 (88)
       (Increase) decrease in other assets...............................             160                (870)
       Increase (decrease) in accounts payable and other liabilities.....          (2,665)                344
       Increase (decrease) in deferred revenue...........................          41,903              (4,172)
                                                                            -------------       -------------
       Net cash provided by (used in) operating activities...............          11,953             (37,156)
Cash flows from investing activities:
   Purchases of property and equipment...................................          (9,391)             (6,753)
   Proceeds from disposal of property and equipment......................             123                  15
   Decrease in restricted cash...........................................              --              14,372
   Purchases of investments..............................................        (116,120)           (147,103)
   Maturities of investments.............................................         121,891             173,720
                                                                            -------------       -------------
       Net cash provided by (used in) investing activities...............          (3,497)             34,251
Cash flows from financing activities:
   Proceeds from issuance of common stock................................             563               1,577
   Proceeds from debt borrowings.........................................              --              34,000
   Repayment of debt borrowings..........................................            (511)            (52,574)
   Repayment of other long-term liabilities..............................              --              (2,466)
                                                                            -------------       -------------
       Net cash provided by (used in) financing activities...............              52             (19,436)
                                                                            -------------       -------------
Net increase (decrease) in cash and cash equivalents.....................           8,508             (22,341)
Cash and cash equivalents at beginning of period.........................          14,612              35,856
                                                                            -------------       -------------
Cash and cash equivalents at end of period...............................   $      23,120       $      13,515
                                                                            =============       =============

Supplemental disclosure of cash flow information:
   Cash paid for interest................................................   $       2,095       $       1,281

Supplemental disclosure of non-cash investing and financing activities:
   Unrealized loss on investments........................................   $         (54)      $           -
   Reversal of deferred stock compensation, in connection
     with stock options..................................................   $          35       $          47
   Retirement of property and equipment..................................   $       4,327       $         298


  The accompanying notes are an integral part of these consolidated financial
                                   statements.

                                       5


                          LEXICON GENETICS INCORPORATED

                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                   (UNAUDITED)

1. BASIS OF PRESENTATION

      The accompanying unaudited consolidated financial statements of Lexicon
Genetics Incorporated (Lexicon or the Company) have been prepared in accordance
with generally accepted accounting principles for interim financial information
and pursuant to the rules and regulations of the Securities and Exchange
Commission (SEC). Accordingly, they do not include all of the information and
footnotes required by generally accepted accounting principles for complete
financial statements.

      In the opinion of management, all adjustments (consisting of normal
recurring adjustments) considered necessary for a fair presentation have been
included. Operating results for the nine-month period ended September 30, 2005
are not necessarily indicative of the results that may be expected for the year
ended December 31, 2005.

      The accompanying consolidated financial statements include the accounts of
Lexicon and its subsidiaries. Intercompany transactions and balances are
eliminated in consolidation.

      For further information, refer to the financial statements and footnotes
thereto included in Lexicon's annual report on Form 10-K for the year ended
December 31, 2004, as filed with the SEC.

2. RECLASSIFICATION

      As of September 30, 2004 and December 31, 2003, Lexicon reclassified
auction rate securities of $53.6 million and $46.1 million, respectively, from
cash equivalents to short-term investments and, as of December 31, 2003, Lexicon
reclassified $42.6 million from restricted cash to short-term investments. The
accompanying consolidated statement of cash flows for the nine months ended
September 30, 2004 has been adjusted to reflect these reclassifications.

3. COMPREHENSIVE LOSS

      Comprehensive loss is comprised of net loss and unrealized gains and
losses on short-term investments, which are considered available-for-sale
securities. Comprehensive loss for the three months ended September 30, 2005 was
$14.2 million, which includes a net loss of $14.1 million and a $33,000
unrealized loss on short-term investments. Comprehensive loss for the nine
months ended September 30, 2005 was $42.3 million, which includes a net loss of
$42.2 million and a $54,000 unrealized loss on short-term investments.

4. NET LOSS PER SHARE

      Net loss per share is computed using the weighted average number of shares
of common stock outstanding during the applicable period. Shares associated with
stock options and warrants are not included because they are antidilutive. There
are no differences between basic and diluted net loss per share for all periods
presented.

                                       6


5. STOCK-BASED COMPENSATION

      Lexicon's stock-based compensation plans are accounted for under the
recognition and measurement provisions of Accounting Principles Board (APB)
Opinion No. 25, "Accounting for Stock Issued to Employees, and Related
Interpretations." Under the intrinsic value method described in APB Opinion No.
25, no compensation expense is recognized if the exercise price of the employee
stock option equals the market price of the underlying stock on the date of
grant. Lexicon recognized stock-based compensation expense of $0.8 million for
the nine months ended September 30, 2004, primarily relating to option grants
made prior to Lexicon's April 2000 initial public offering. All deferred stock
compensation relating to these options was fully amortized as of January 31,
2004 when these options became fully vested.

      The following table illustrates the effect on net loss and net loss per
share if the fair value recognition provisions of Financial Accounting Standards
Board (FASB) Statement of Financial Accounting Standards (SFAS) No. 123
"Accounting for Stock Based Compensation," had been applied to all outstanding
and unvested awards in each period:



                                                              THREE MONTHS ENDED             NINE MONTHS ENDED
                                                                  SEPTEMBER 30,                 SEPTEMBER 30,
                                                       ------------------------------  ---------------------------
                                                            2005            2004           2005          2004
                                                       --------------  --------------  ------------   ------------
                                                                                          
Net loss, as reported:..............................   $     (14,121)  $     (14,377)  $   (42,229)   $   (46,631)
Add: Stock-based employee compensation
   expense included in reported net loss............               -               -           (20)           827
Deduct: Total stock-based employee compensation
   expense determined under fair value based
   method for all awards............................          (2,679)         (3,842)       (8,936)       (12,590)
                                                       -------------   -------------   -----------    -----------
Pro forma net loss..................................   $     (16,800)  $     (18,219)  $   (51,185)   $   (58,394)
                                                       =============   =============   ===========    ===========
Net loss per common share, basic and diluted
   As reported......................................   $       (0.22)  $       (0.23)  $     (0.66)   $     (0.74)
                                                       =============   =============   ===========    ===========
   Pro forma........................................   $       (0.26)  $       (0.29)  $     (0.80)   $     (0.92)
                                                       =============   =============   ===========    ===========


6. DEBT OBLIGATIONS

      Genentech Loan: On December 31, 2002, Lexicon borrowed $4.0 million under
a note agreement with Genentech, Inc. The proceeds of the loan are to be used to
fund research efforts under the alliance agreement with Genentech. The note
matures on December 31, 2005, but the Company may prepay it at any time. The
Company may repay the note, at its option, in cash, in shares of common stock
valued at the then-current market price, or in a combination of cash and shares,
subject to certain limitations. The note accrues interest at an annual rate of
8%, compounded quarterly.

      Mortgage Loan: In April 2004, Lexicon purchased its facilities in The
Woodlands, Texas that were previously subject to a synthetic lease. The Company
repaid the $54.8 million funded under the synthetic lease with proceeds from a
$34.0 million third-party mortgage financing and $20.8 million in cash. The
mortgage loan has a ten-year term with a 20-year amortization and bears interest
at a fixed rate of 8.23%. As a result of the refinancing, all restrictions on
the cash and investments that had secured the obligations under the synthetic
lease were eliminated.

7. COMMITMENTS AND CONTINGENCIES

      In May 2002, Lexicon's subsidiary Lexicon Pharmaceuticals (New Jersey),
Inc. leased a 76,000 square-foot laboratory and office space in Hopewell, New
Jersey under an agreement which expires in June 2013. The lease provides for an
escalating yearly rent payment of $1.3 million in the first year,

                                       7


$2.1 million in years two and three, $2.2 million in years four to six, $2.3
million in years seven to nine and $2.4 million in years ten and eleven. Lexicon
is the guarantor of the obligations of its subsidiary under the lease. The
Company is required to maintain restricted investments to collateralize the
Hopewell lease. As of September 30, 2005, the Company had $430,000 in restricted
investments to collateralize a standby letter of credit for this lease.

8. NEW AGREEMENT

      In July 2005, Lexicon was awarded $35 million from the Texas Enterprise
Fund for the creation of a knockout mouse embryonic stem cell library containing
350,000 cell lines using Lexicon's proprietary gene trapping technology. Lexicon
will create the library for the Texas Institute for Genomic Medicine (TIGM), a
newly formed non-profit institute whose founding members are Texas A&M
University, the Texas A&M University System Health Science Center and Lexicon.
TIGM researchers may also access specific cells from Lexicon's current gene trap
library of 270,000 mouse embryonic stem cell lines and will have certain rights
to utilize Lexicon's patented gene targeting technologies. In addition, Lexicon
will equip TIGM with the bioinformatics software required for the management and
analysis of data relating to the library. The Texas Enterprise Fund has also
awarded $15 million to the Texas A&M University System for the creation of
facilities and infrastructure to house the library.

      Under the terms of the award, Lexicon is responsible for the creation of a
specified number of jobs, reaching an aggregate of 1,616 new jobs in Texas by
December 31, 2015. Lexicon will obtain credits based on funding received by TIGM
and certain related parties from sources other than the State of Texas that it
may offset against its potential liability for any job creation shortfalls.
Lexicon will also obtain credits against future jobs commitment liabilities for
any surplus jobs it creates. Subject to these credits, if Lexicon fails to
create the specified number of jobs, the state may require Lexicon to repay
$2,415 for each job Lexicon falls short. Lexicon's maximum aggregate exposure
for such payments, if Lexicon fails to create any new jobs, is approximately
$14.4 million, without giving effect to any credits to which Lexicon may be
entitled. The Texas A&M University System, together with TIGM, has independent
job creation obligations and is obligated for an additional period to maintain
an aggregate of 5,000 jobs, inclusive of those Lexicon creates.

                                       8


ITEM 2.   MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND
          RESULTS OF OPERATIONS

OVERVIEW

      We are a biopharmaceutical company focused on discovering and developing
breakthrough treatments for human disease. We are using gene knockout technology
to systematically discover the physiological functions of genes in living
mammals, or in vivo. We generate our gene function discoveries using knockout
mice - mice whose DNA has been altered to disrupt, or "knock out," the function
of the altered gene. Our patented gene trapping and gene targeting technologies
enable us to rapidly generate these knockout mice by altering the DNA of genes
in a special variety of mouse cells, called embryonic stem cells, which can be
cloned and used to generate mice with the altered gene. We employ an integrated
platform of advanced medical technologies to systematically discover and
validate which genes, when knocked out, result in a favorable medical profile
with pharmaceutical utility. We then pursue those genes and the proteins they
encode as potential targets for therapeutic intervention in our drug discovery
programs.

      We employ internal resources and drug discovery alliances to discover
potential small molecule, antibody and protein drugs for in vivo-validated drug
targets that we consider to have high pharmaceutical value. We use our own
sophisticated libraries of drug-like chemical compounds and an industrialized
medicinal chemistry platform to identify small molecule drug candidates for our
in vivo-validated drug targets. We have established alliances with Bristol-Myers
Squibb Company to discover and develop novel small molecule drugs in the
neuroscience field; with Genentech, Inc. to discover therapeutic proteins and
antibody targets; with N.V. Organon to discover, develop and commercialize novel
biotherapeutics; and with Takeda Pharmaceutical Company Limited to discover new
drugs for the treatment of high blood pressure. In addition, we have established
collaborations and license agreements with many other leading pharmaceutical and
biotechnology companies under which we receive fees and, in some cases, are
eligible to receive milestone and royalty payments, for access to some of our
technologies and discoveries for use in their own drug discovery efforts.

      We derive substantially all of our revenues from drug discovery alliances,
target validation collaborations for the development and, in some cases,
analysis of the physiological effects of genes altered in knockout mice and
technology licenses. To date, we have generated a substantial portion of our
revenues from a limited number of sources.

      Our operating results and, in particular, our ability to generate
additional revenues are dependent on many factors, including our success in
establishing research collaborations and technology licenses, expirations of our
research collaborations, the success rate of our discovery efforts leading to
opportunities for new research collaborations and licenses, as well as milestone
payments and royalties, the timing and willingness of collaborators to
commercialize products which may result in royalties, and general and
industry-specific economic conditions which may affect research and development
expenditures. Our future revenues from collaborations and alliances are
uncertain because our existing agreements have fixed terms or relate to specific
projects of limited duration. Our future revenues from technology licenses are
uncertain because they depend, in large part, on securing new agreements.
Subject to limited exceptions, we do not intend to offer subscriptions to our
databases or make our compound libraries available for purchase in the future.
Our ability to secure future revenue-generating agreements will depend upon our
ability to address the needs of our potential future collaborators and
licensees, and to negotiate agreements that we believe are in our long-term best
interests. We may determine that our interests are better served by retaining
rights to our discoveries and advancing our therapeutic programs to a later
stage, which could limit our near-term revenues. Because of these and other
factors, our operating results have fluctuated in the past and are likely to do
so in the future, and we

                                       9


do not believe that period-to-period comparisons of our operating results are a
good indication of our future performance.

      Since our inception, we have incurred significant losses and, as of
September 30, 2005, we had an accumulated deficit of $303.3 million. Our losses
have resulted principally from costs incurred in research and development,
general and administrative costs associated with our operations, and non-cash
stock-based compensation expenses associated with stock options granted to
employees and consultants prior to our April 2000 initial public offering.
Research and development expenses consist primarily of salaries and related
personnel costs, material costs, facility costs, depreciation on property and
equipment, legal expenses resulting from intellectual property prosecution and
other expenses related to our drug discovery and Genome5000 programs, the
development and analysis of knockout mice and our other target validation
research efforts, and the development of compound libraries. General and
administrative expenses consist primarily of salaries and related expenses for
executive, finance and other administrative personnel, professional fees and
other corporate expenses, including information technology, facilities costs and
general legal activities. In connection with the expansion of our drug discovery
programs and our target validation research efforts, we expect to incur
increasing research and development and general and administrative costs. As a
result, we will need to generate significantly higher revenues to achieve
profitability.

CRITICAL ACCOUNTING POLICIES

Revenue Recognition

      We recognize revenues when persuasive evidence of an arrangement exists,
delivery has occurred or services have been rendered, the price is fixed and
determinable, and collectibility is reasonably assured. Payments received in
advance under these arrangements are recorded as deferred revenue until earned.

      Upfront fees and annual research funding under our drug discovery
alliances are recognized as revenue on a straight-line basis over the estimated
period of service, generally the contractual research term, to the extent they
are non-refundable. Milestone-based fees are recognized upon completion of
specified milestones according to contract terms. Fees for access to our
databases and other target validation resources are recognized ratably over the
subscription or access period. Payments received under target validation
collaborations and government grants are recognized as revenue as we perform our
obligations related to such research to the extent such fees are non-refundable.
Non-refundable technology license fees are recognized as revenue upon the grant
of the license, when performance is complete and there is no continuing
involvement.

      Revenues recognized from multiple element contracts are allocated to each
element of the arrangement based on the relative fair value of the elements. The
determination of fair value of each element is based on objective evidence. When
revenues for an element are specifically tied to a separate earnings process,
revenue is recognized when the specific performance obligation associated with
the element is completed. When revenues for an element are not specifically tied
to a separate earnings process, they are recognized ratably over the term of the
agreement.

      A change in our revenue recognition policy or changes in the terms of
contracts under which we recognize revenues could have an impact on the amount
and timing of our recognition of revenues.

                                       10


Research and Development Expenses

      Research and development expenses consist of costs incurred for
company-sponsored as well as collaborative research and development activities.
These costs include direct and research-related overhead expenses and are
expensed as incurred. Patent costs and technology license fees for technologies
that are utilized in research and development and have no alternative future use
are expensed when incurred.

      Prior to preclinical development work, we are unable to segregate the
costs related to research performed on drug candidates because the drug
candidate is often not specifically identified until the later stages of our
research. With the commencement of formal preclinical development in 2005, we
will account on a program-by-program basis for the costs related to the
development of the identified drug products.

Goodwill Impairment

      Goodwill is not amortized, but is tested at least annually for impairment
at the reporting unit level. We have determined that the reporting unit is the
single operating segment disclosed in our current financial statements.
Impairment is the condition that exists when the carrying amount of goodwill
exceeds its implied fair value. The first step in the impairment process is to
determine the fair value of the reporting unit and then compare it to the
carrying value, including goodwill. We determined that the market capitalization
approach is the most appropriate method of measuring fair value of the reporting
unit. Under this approach, fair value is calculated as the average closing price
of our common stock for the 30 days preceding the date that the annual
impairment test is performed, multiplied by the number of outstanding shares on
that date. A control premium, which is representative of premiums paid in the
marketplace to acquire a controlling interest in a company, is then added to the
market capitalization to determine the fair value of the reporting unit. If the
fair value exceeds the carrying value, no further action is required and no
impairment loss is recognized. Additional impairment assessments may be
performed on an interim basis if we encounter events or changes in circumstances
that would indicate that, more likely than not, the carrying value of goodwill
has been impaired.

RESULTS OF OPERATIONS

Three Months Ended September 30, 2005 and 2004

      Revenues. Total revenues and dollar and percentage changes as compared to
the corresponding period in the prior year are as follows (dollar amounts are
presented in millions):



                                            THREE MONTHS ENDED SEPTEMBER 30,
                                            --------------------------------
                                              2005                     2004
                                            -------                   ------
                                                                
Total revenues...........................   $  14.0                   $ 13.1
Dollar increase..........................   $   0.9
Percentage increase......................         7%


         -     Collaborative research - Revenue from collaborative research
               increased 18% to $13.5 million primarily due to our recognition
               of revenues under our biotherapeutics collaboration with Organon,
               which was entered into in May 2005, and our award from the Texas
               Enterprise Fund for the creation of a knockout mouse embryonic
               stem cell library, which was entered into in July 2005. This was
               offset in part by the recognition in the prior year period of a
               performance milestone under our therapeutic protein and antibody
               target discovery alliance with Genentech.

                                       11


            -     Subscription and license fees - Revenue from subscriptions and
                  license fees decreased 73% to $0.4 million primarily as a
                  result of our termination in December 2004, of the
                  collaboration term under our LexVision(R) database
                  subscription program with Bristol-Myers Squibb.

      Research and Development Expenses. Research and development expenses and
dollar and percentage changes as compared to the corresponding period in the
prior year are as follows (dollar amounts are presented in millions):



                                           THREE MONTHS ENDED SEPTEMBER 30,
                                           --------------------------------
                                                 2005            2004
                                               -------         -------
                                                         
Total research and development expense...      $  23.3         $  22.5
Dollar increase..........................      $   0.8
Percentage increase......................            4%


      Research and development expenses consist primarily of salaries and other
personnel-related expenses, laboratory supplies, facility and equipment costs,
third-party and other services. The change in the three months ended September
30, 2005 as compared to the corresponding period in 2004 resulted primarily from
the following costs:

            -     Personnel - Personnel costs increased 5% to $11.5 million
                  primarily due to increased personnel to support the expansion
                  of our drug discovery programs and merit-based pay increases
                  for employees. Salaries, bonuses, employee benefits, payroll
                  taxes, and recruiting and relocation costs are included in
                  personnel costs.

            -     Laboratory supplies - Laboratory supplies expense decreased
                  18% to $3.2 million due primarily to the bulk purchase of
                  certain supplies in the prior year period.

            -     Facilities and equipment - Facilities and equipment costs
                  increased 7% to $5.2 million due primarily to higher utility
                  costs.

            -     Third-party services - Costs associated with third-party
                  services increased 44% to $2.0 million primarily due to an
                  increase in third-party contract research costs. Costs
                  associated with third-party services include third-party
                  contract research, subscriptions to third-party databases,
                  technology licenses, and legal and patent fees.

            -     Other - Other costs increased by 4% to $1.4 million primarily
                  related to increased information technology costs.

      General and Administrative Expenses. General and administrative expenses
and dollar and percentage changes as compared to the corresponding period in the
prior year are as follows (dollar amounts are presented in millions):



                                             THREE MONTHS ENDED SEPTEMBER 30,
                                             --------------------------------
                                                  2005             2004
                                                 -------          ------
                                                            
Total general and administrative expense..       $   4.7          $  4.6
Dollar increase...........................       $   0.1
Percentage increase.......................             2%


      General and administrative expenses consist primarily of personnel costs
to support our research activities, facility and equipment costs and
professional fees, such as legal fees. The change in the three months ended
September 30, 2005 as compared to the corresponding period in 2004 resulted
primarily from the following costs:

                                       12


            -     Personnel - Personnel costs increased 10% to $2.9 million due
                  to increased personnel and merit-based pay increases for
                  employees. Salaries, bonuses, employee benefits, payroll
                  taxes, recruiting and relocation costs are included in
                  personnel costs.

            -     Facilities and equipment - Facilities and equipment costs
                  increased 7% to $0.8 million due primarily to higher utility
                  costs.

            -     Professional fees - Professional fees decreased 24% to $0.4
                  million primarily due to lower legal fees.

            -     Other - Other costs decreased 12% to $0.6 million.

      Interest Income. Interest income increased 89% to $0.8 million in the
three months ended September 30, 2005 from $0.4 million in the corresponding
period in 2004 due to higher interest rates and higher average cash and
investment balances.

      Interest Expense. Interest expense remained unchanged at $0.8 million in
the three months ended September 30, 2005 and 2004.

      Net Loss and Net Loss Per Common Share. Net loss decreased 2% to $14.1
million in the three months ended September 30, 2005 from $14.4 million in the
corresponding period in 2004. Net loss per common share decreased to $0.22 in
the three months ended September 30, 2005 from $0.23 in the corresponding period
in 2004.

      Our quarterly operating results have fluctuated in the past and are likely
to do so in the future, and we believe that quarter-to-quarter comparisons of
our operating results are not a good indication of our future performance.

Nine Months Ended September 30, 2005 and 2004

      Revenues. Total revenues and dollar and percentage changes as compared to
the corresponding period in the prior year are as follows (dollar amounts are
presented in millions):



                                             NINE MONTHS ENDED SEPTEMBER 30,
                                             -------------------------------
                                                 2005              2004
                                                -------           ------
                                                            
Total revenues...........................       $  41.8           $ 35.7
Dollar increase..........................       $   6.1
Percentage increase......................            17%


            -     Collaborative research - Revenue from collaborative research
                  increased 29% to $36.2 million primarily due to our
                  recognition of revenues under our biotherapeutics
                  collaboration with Organon, which was entered into in May
                  2005, our hypertension drug discovery alliance with Takeda,
                  which was entered into in July 2004, and our award from the
                  Texas Enterprise Fund for the creation of a knockout mouse
                  embryonic stem cell library. This was offset in part by the
                  recognition in the prior year period of a performance
                  milestone under our therapeutic protein and antibody target
                  discovery alliance with Genentech and a decrease in revenues
                  from the termination of our therapeutic protein discovery
                  alliance with Incyte in June 2004.

            -     Subscription and license fees - Revenue from subscriptions and
                  license fees decreased 27% to $5.6 million primarily as a
                  result of the termination in June 2004 and December 2004,
                  respectively, of the collaboration term under our LexVision
                  database subscription programs with Incyte Corporation and
                  Bristol-Myers Squibb. The reduction was offset in

                                       13


            part by technology license fees received from Deltagen, Inc. in
            connection with the settlement of Lexicon's claim in Deltagen's
            bankruptcy proceedings.

      Research and Development Expenses. Research and development expenses and
dollar and percentage changes as compared to the corresponding period in the
prior year are as follows (dollar amounts are presented in millions):



                                            NINE MONTHS ENDED SEPTEMBER 30,
                                            -------------------------------
                                                 2005            2004
                                                -------         -------
                                                          
Total research and development expense...       $  69.8         $  67.5
Dollar increase..........................       $   2.3
Percentage increase......................             3%


      Research and development expenses consist primarily of salaries and other
personnel-related expenses, laboratory supplies, facility and equipment costs,
third-party and other services. The change in the nine months ended September
30, 2005 as compared to the corresponding period in 2004 resulted primarily from
the following costs:

            -     Personnel - Personnel costs increased 8% to $34.9 million
                  primarily due to increased personnel to support the expansion
                  of our drug discovery programs and merit-based pay increases
                  for employees.

            -     Laboratory supplies - Laboratory supplies expense decreased
                  11% to $9.6 million due primarily to the bulk purchase of
                  certain supplies in the prior year period.

            -     Facilities and equipment - Facilities and equipment costs
                  increased 4% to $15.6 million primarily due to higher utility
                  costs.

            -     Third-party services - Costs associated with third-party
                  services increased 4% to $5.4 million primarily due to an
                  increase in third-party contract research costs, offset in
                  part by the termination in June 2004 of our LifeSeq(R) Gold
                  database subscription.

            -     Other - Other costs increased by 12% to $4.1 million primarily
                  related to increased information technology costs.

      General and Administrative Expenses. General and administrative expenses
and dollar and percentage changes as compared to the corresponding period in the
prior year are as follows (dollar amounts are presented in millions):



                                              NINE MONTHS ENDED SEPTEMBER 30,
                                              -------------------------------
                                                  2005             2004
                                                 -------          ------
                                                            
Total general and administrative expense..       $  13.9          $ 14.3
Dollar decrease...........................       $   0.4
Percentage decrease.......................             3%


      General and administrative expenses consist primarily of personnel costs
to support our research activities, facility and equipment costs and
professional fees, such as legal fees. The change in the nine months ended
September 30, 2005 as compared to the corresponding period in 2004 resulted
primarily from the following costs:

            -     Personnel - Personnel costs increased 2% to $8.3 million.

            -     Facilities and equipment - Facilities and equipment costs
                  remain unchanged at $2.3 million.

                                       14


            -     Professional fees - Professional fees decreased 5% to $1.4
                  million primarily due to decreased legal fees.

            -     Other - Other costs decreased 4% to $1.8 million.

      Interest Income. Interest income increased 47% to $1.8 million in the nine
months ended September 30, 2005 from $1.2 million in the corresponding period in
2004 primarily due to higher interest rates and higher average cash and
investment balances.

      Interest Expense. Interest expense increased to $2.5 million in the nine
months ended September 30, 2005 from $1.8 million in the corresponding period in
2004. The increase was attributable to interest expense on the $34.0 million
mortgage loan on our facilities in The Woodlands, Texas, which was entered into
in April 2004.

      Net Loss and Net Loss Per Common Share. Net loss decreased 9% to $42.2
million in the nine months ended September 30, 2005 from $46.6 million in the
corresponding period in 2004. Net loss per common share decreased to $0.66 in
the nine months ended September 30, 2005 from $0.74 in the corresponding period
in 2004. Net loss includes stock-based compensation expense of $0.8 million in
the nine months ended September 30, 2004.

LIQUIDITY AND CAPITAL RESOURCES

      We have financed our operations from inception primarily through sales of
common and preferred stock, contract and milestone payments to us under our drug
discovery alliance, target validation, database subscription and license
agreements, equipment financing arrangements and leasing arrangements. From our
inception through September 30, 2005, we had received net proceeds of $295.4
million from issuances of common and preferred stock, including $203.2 million
of net proceeds from the initial public offering of our common stock in April
2000 and $50.1 million from our July 2003 common stock offering. In addition,
from our inception through September 30, 2005, we received $312.3 million in
cash payments from drug discovery alliances, target validation collaborations,
database subscription and technology license fees, sales of compound libraries
and reagents, and government grants, of which $234.9 million had been recognized
as revenues through September 30, 2005.

      As of September 30, 2005, we had $90.2 million in cash, cash equivalents
and short-term investments (including $0.4 million of restricted investments),
as compared to $87.6 million (including $0.4 million of restricted investments)
as of December 31, 2004. Cash provided by operating activities was $12.0 million
in the nine months ended September 30, 2005. This consisted primarily of the net
loss for the period of $42.2 million offset by non-cash charges of $7.8 million
related to depreciation expense and $0.9 million related to amortization of
intangible assets other than goodwill; a $41.9 million increase in deferred
revenue; and changes in other operating assets and liabilities of $3.6 million.
Cash used in investing activities was $3.5 million in the nine months ended
September 30, 2005, primarily due to purchases of property and equipment of $9.4
million offset by net maturities of short-term investments of $5.8 million.

      In April 2004, we purchased our facilities in The Woodlands, Texas from
the lessor under our previous synthetic lease agreement. In connection with such
purchase, we repaid the $54.8 million funded under the synthetic lease with
proceeds from a $34.0 million third-party mortgage financing and $20.8 million
in cash. The mortgage loan has a ten-year term with a 20-year amortization and
bears interest at a fixed rate of 8.23%. As a result of the refinancing, all
restrictions on the cash and investments that had secured our obligations under
the synthetic lease were eliminated.

                                       15


      In May 2002, our subsidiary Lexicon Pharmaceuticals (New Jersey), Inc.
signed a ten-year lease for a 76,000 square-foot facility in Hopewell, New
Jersey. The term of the lease extends until June 30, 2013. The lease provides
for an escalating yearly base rent payment of $1.3 million in the first year,
$2.1 million in years two and three, $2.2 million in years four to six, $2.3
million in years seven to nine and $2.4 million in years ten and eleven. We are
the guarantor of the obligations of our subsidiary under the lease.

      In December 2002, we borrowed $4.0 million under a note agreement with
Genentech. The proceeds of the loan are to be used to fund research efforts
under our alliance with Genentech for the discovery of therapeutic proteins and
antibody targets. The note matures on or before December 31, 2005, but we may
prepay it at any time. We may repay the note, at our option, in cash, in shares
of our common stock valued at the then-current market value, or in a combination
of cash and shares, subject to certain limitations. The note accrues interest at
an annual rate of 8%, compounded quarterly.

      In July 2005, we were awarded $35 million from the Texas Enterprise Fund
for the creation of a knockout mouse embryonic stem cell library containing
350,000 cell lines. We will create the library for the Texas Institute for
Genomic Medicine, a newly formed non-profit institute whose founding members are
Texas A&M University, the Texas A&M University System Health Science Center and
us. Under the terms of the award, we are responsible for the creation of a
specified number of jobs, reaching an aggregate of 1,616 new jobs in Texas by
December 31, 2015. We will obtain credits based on funding received by the
institute and certain related parties from sources other than the State of Texas
that we may offset against our potential liability for any job creation
shortfalls. We will also obtain credits against future jobs commitment
liabilities for any surplus jobs we create. Subject to these credits, if we fail
to create the specified number of jobs, the state may require us to repay $2,415
for each job we fall short. Our maximum aggregate exposure for such payments, if
we fail to create any new jobs, is approximately $14.4 million, without giving
effect to any credits to which we may be entitled.

      Our future capital requirements will be substantial and will depend on
many factors, including our ability to obtain alliance, collaboration and
technology license agreements, the amount and timing of payments under such
agreements, the level and timing of our research and development expenditures,
market acceptance of our products, the resources we devote to developing and
supporting our products and other factors. Our capital requirements will also be
affected by any expenditures we make in connection with license agreements and
acquisitions of and investments in complementary technologies and businesses. We
expect to devote substantial capital resources to continue our research and
development efforts, to expand our support and product development activities,
and for other general corporate activities. We believe that our current
unrestricted cash and investment balances and revenues we expect to derive from
drug discovery alliances, target validation collaborations and technology
licenses will be sufficient to fund our operations through approximately the
next two years. During or after this period, if cash generated by operations is
insufficient to satisfy our liquidity requirements, we will need to sell
additional equity or debt securities or obtain additional credit arrangements.
Additional financing may not be available on terms acceptable to us or at all.
The sale of additional equity or convertible debt securities may result in
additional dilution to our stockholders.

DISCLOSURE ABOUT MARKET RISK

      We are exposed to limited market and credit risk on our cash equivalents,
which have maturities of three months or less at the time of purchase. We
maintain a short-term investment portfolio which consists of U.S. government
agency debt obligations, investment grade commercial paper, corporate debt
securities and certificates of deposit that mature within twelve months and
auction rate securities that mature greater than twelve months from the time of
purchase, which we believe are subject to limited

                                       16


market and credit risk. We currently do not hedge interest rate exposure or hold
any derivative financial instruments in our investment portfolio.

      We have operated primarily in the United States and substantially all
sales to date have been made in U.S. dollars. Accordingly, we have not had any
material exposure to foreign currency rate fluctuations.

RISK FACTORS

      Our business is subject to certain risks and uncertainties, including
those referenced below:

Risks Related to Our Company and Business

   -  we have a history of net losses, and we expect to continue to incur net
      losses and may not achieve or maintain profitability

   -  we will need additional capital in the future and, if it is not available,
      we will have to curtail or cease operations

   -  any sale of additional equity securities in the future may be dilutive to
      our stockholders

   -  we are an early-stage company, and we may not successfully develop or
      commercialize any therapeutics or drug targets that we have identified

   -  we face substantial competition in the discovery of the DNA sequences of
      genes and their functions and in our drug discovery and product
      development efforts

   -  we rely heavily on our collaborators to develop and commercialize
      pharmaceutical products based on genes that we identify as promising
      candidates for development as drug targets, and our collaborators' efforts
      may fail to yield pharmaceutical products on a timely basis, if at all

   -  we rely on several key collaborators for a significant portion of our
      revenues, the loss of any of which would negatively impact our business to
      the extent such losses are not offset by additional collaborators

   -  cancellations by or conflicts with our collaborators could harm our
      business

   -  we may be unsuccessful in developing and commercializing pharmaceutical
      products on our own

   -  we lack the capability to manufacture materials for preclinical studies,
      clinical trials or commercial sales and will rely on third parties to
      manufacture our potential products, which may harm or delay our product
      development and commercialization efforts

   -  we may engage in future acquisitions, which may be expensive and time
      consuming and from which we may not realize anticipated benefits

   -  if we lose our key personnel or are unable to attract and retain
      additional personnel, we may be unable to pursue collaborations or develop
      our own products

   -  any contamination among our knockout mouse population could negatively
      affect the reliability of our scientific research or cause us to incur
      significant remedial costs

   -  because all of our target validation operations are located at a single
      facility, the occurrence of a disaster could significantly disrupt our
      business

                                       17


   -  our operating results have been and likely will continue to fluctuate, and
      we believe that period-to-period comparisons of our operating results are
      not a good indication of our future performance

Risks Related to Our Industry

   -  our ability to patent our inventions is uncertain because patent laws and
      their interpretation are highly uncertain and subject to change

   -  our patent applications may not result in enforceable patent rights and,
      as a result, the protection afforded to our scientific discoveries may be
      insufficient

   -  if other companies and institutions obtain patents relating to our drug
      target or product candidate discoveries, we may be unable to obtain
      patents for our inventions based upon those discoveries and may be blocked
      from using or developing some of our technologies and products

   -  issued or pending patents may not fully protect our discoveries, and our
      competitors may be able to commercialize technologies or products similar
      to those covered by our issued or pending patents

   -  we may be involved in patent litigation and other disputes regarding
      intellectual property rights and may require licenses from third parties
      for our discovery and development and planned commercialization
      activities, and we may not prevail in any such litigation or other dispute
      or be able to obtain required licenses

   -  we use intellectual property that we license from third parties, and if we
      do not comply with these licenses, we could lose our rights under them

   -  we have not sought patent protection outside of the United States for some
      of our inventions, and some of our licensed patents only provide coverage
      in the United States, and as a result, our international competitors could
      be granted foreign patent protection with respect to our discoveries

   -  we may be unable to protect our trade secrets

   -  our efforts to discover, evaluate and validate potential targets for drug
      intervention and our drug discovery programs are subject to evolving data
      and other risks inherent in the drug discovery process

   -  our industry is subject to extensive and uncertain government regulatory
      requirements, which could significantly hinder our ability, or the ability
      of our collaborators, to obtain, in a timely manner or at all, government
      approval of products based on genes that we identify, or to commercialize
      such products

   -  if our potential products receive regulatory approval, we or our
      collaborators will remain subject to extensive and rigorous ongoing
      regulation

   -  the uncertainty of pharmaceutical pricing and reimbursement may decrease
      the commercial potential of any products that we or our collaborators may
      develop and affect our ability to raise capital

   -  we use hazardous chemicals and radioactive and biological materials in our
      business; any disputes relating to improper handling, storage or disposal
      of these materials could be time consuming and costly

                                       18


   -  we may be sued for product liability

   -  public perception of ethical and social issues may limit or discourage the
      use of our technologies, which could reduce our revenues

         For additional discussion of the risks and uncertainties that affect
our business, see "Item 1. Business - Risk Factors" included in our annual
report on Form 10-K for the year ended December 31, 2004, as filed with the
Securities and Exchange Commission.

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

      See "Disclosure about Market Risk" under "Item 2. Management's Discussion
and Analysis of Financial Condition and Results of Operations" for quantitative
and qualitative disclosures about market risk.

ITEM 4. CONTROLS AND PROCEDURES

      Our chief executive officer and chief financial officer have concluded
that our disclosure controls and procedures (as defined in rules 13a-15(e) and
15d-15(e) under the Securities Exchange Act of 1934 (the "Exchange Act")) are
sufficiently effective to ensure that the information required to be disclosed
by us in the reports we file under the Exchange Act is gathered, analyzed and
disclosed with adequate timeliness, accuracy and completeness, based on an
evaluation of such controls and procedures as of the end of the period covered
by this report.

      Subsequent to our evaluation, there were no significant changes in
internal controls or other factors that could significantly affect internal
controls, including any corrective actions with regard to significant
deficiencies and material weaknesses.

                                       19


PART II OTHER INFORMATION

ITEM 5. OTHER INFORMATION

      On October 26, 2005, the compensation committee of our Board of Directors
approved an additional annual retainer of $15,000 for service as non-executive
Chairman of our Board of Directors. All non-employee directors currently receive
an annual retainer of $15,000 for their service on the Board of Directors.

      On October 26, 2005, the compensation committee also approved an
additional annual option grant to the non-executive Chairman of our Board of
Directors under our 2000 Equity Incentive Plan to purchase 10,000 shares of
common stock at an exercise price equal to the fair market value of our common
stock on the date of grant. All non-employee directors who have served in such
capacity for six months currently receive an annual option to purchase 10,000
shares of common stock under our 2000 Non-Employee Directors' Stock Option Plan
at an exercise price equal to the fair market value of our common stock on the
date of grant.

ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K

      (a)   Exhibits



EXHIBIT NO.                               DESCRIPTION
- -----------  -------------------------------------------------------------------
          
    10.1     --  Economic Development Agreements dated July 15, 2005, with the
                 State of Texas and the Texas A&M University System

   +10.2     --  Collaboration and License Agreement, dated July 15, 2005, with
                 the Texas A&M University System and the Texas Institute for
                 Genomic Medicine

    10.3     --  Non-Employee Director Compensation

    31.1     --  Certification of CEO Pursuant to Section 302 of the Sarbanes-
                 Oxley Act of 2002

    31.2     --  Certification of CFO Pursuant to Section 302 of the Sarbanes-
                 Oxley Act of 2002

    32.1     --  Certification of CEO and CFO Pursuant to Section 906 of the
                 Sarbanes-Oxley Act of 2002


      +  Confidential treatment has been requested for a portion of this
         exhibit. The confidential portions of this exhibit have been omitted
         and filed separately with the Securities and Exchange Commission

      (b)   Reports on Form 8-K:

      On July 18, 2005, we filed a Current Report on Form 8-K dated July 15,
2005 related to our entry into an Economic Development Agreement, dated July 15,
2005 with the State of Texas and the Texas A&M University System and a
Collaboration and License Agreement, dated July 15, 2005, with the Texas A&M
University System and the Texas Institute for Genomic Medicine.

      On July 28, 2005, we filed a Current Report on Form 8-K dated July 28,
2005 related to our issuance of a press release reporting our financial results
for the quarter ended June 30, 2005, which press release included our
consolidated balance sheet data and consolidated statements of operations data
for the period.

                                       20


                                   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:  November 1, 2005       By:      /s/ Arthur T. Sands
                                 -----------------------------------------------
                                     Arthur T. Sands, M.D., Ph.D.
                                     President and Chief Executive Officer

Date:  November 1, 2005       By:      /s/ Julia P. Gregory
                                 -----------------------------------------------
                                     Julia P. Gregory

                                     Executive Vice President, Corporate
                                     Development and Chief Financial Officer

                                       21


                                INDEX TO EXHIBITS



EXHIBIT NO.                               DESCRIPTION
- -----------  -------------------------------------------------------------------
          
    10.1     --  Economic Development Agreements dated July 15, 2005, with the
                 State of Texas and the Texas A&M University System

   +10.2     --  Collaboration and License Agreement, dated July 15, 2005, with
                 the Texas A&M University System and the Texas Institute for
                 Genomic Medicine

    10.3     --  Non-Employee Director Compensation

    31.1     --  Certification of CEO Pursuant to Section 302 of the Sarbanes-
                 Oxley Act of 2002

    31.2     --  Certification of CFO Pursuant to Section 302 of the Sarbanes-
                 Oxley Act of 2002

    32.1     --  Certification of CEO and CFO Pursuant to Section 906 of the
                 Sarbanes-Oxley Act of 2002


    +   Confidential treatment has been requested for a portion of this
        exhibit. The confidential portions of this exhibit have been omitted
        and filed separately with the Securities and Exchange Commission