<PAGE>   1


                                                                   EXHIBIT 10.10


                               ILEX ONCOLOGY, INC.

                          EMPLOYEE STOCK PURCHASE PLAN
                            (effective June 1, 2000)


<PAGE>   2

                                TABLE OF CONTENTS


<TABLE>
<CAPTION>
                                                                                                            SECTION
<S>                                                                                                        <C>

ARTICLE I - PURPOSE, COMMITMENT AND INTENT

         Purpose................................................................................................1.1
         Term of Plan...........................................................................................1.2
         Share Commitment.......................................................................................1.3
         Intent.................................................................................................1.4
         Shareholder Approval...................................................................................1.5

ARTICLE II - DEFINITIONS

         Affiliate..............................................................................................2.1
         Beneficiary............................................................................................2.2
         Board of Directors.....................................................................................2.3
         Code...................................................................................................2.4
         Committee..............................................................................................2.5
         Company................................................................................................2.6
         Compensation...........................................................................................2.7
         Employee...............................................................................................2.8
         Employer...............................................................................................2.9
         Enrollment Date.......................................................................................2.10
         Exercise Date.........................................................................................2.11
         Fair Market Value or FMV..............................................................................2.12
         Offering Period.......................................................................................2.13
         Option................................................................................................2.14
         Option Price..........................................................................................2.15
         Participant...........................................................................................2.16
         Plan..................................................................................................2.17
         Purchase Period.......................................................................................2.18
         Shares................................................................................................2.19
         Stock.................................................................................................2.20

ARTICLE III - ELIGIBILITY

         General Requirements...................................................................................3.1
         Limitations Upon Participation.........................................................................3.2
</TABLE>


                                       -i-

<PAGE>   3


<TABLE>
<CAPTION>
                                                                                                            SECTION

ARTICLE IV - PARTICIPATION

<S>                                                                                                         <C>
         Grant and Exercise of Option...........................................................................4.1
         Offering Periods.......................................................................................4.2
         Payroll Deduction......................................................................................4.3
         Payroll Deductions Continuing..........................................................................4.4
         Right to Stop and Adjust Payroll Deductions............................................................4.5
         Accounting for Funds...................................................................................4.6
         Employer's Use of Funds................................................................................4.7

ARTICLE V - IN SERVICE WITHDRAWAL, TERMINATION OF EMPLOYMENT, RETIREMENT OR DEATH

         In Service Withdrawal .................................................................................5.1
         Termination of Employment..............................................................................5.2
         Retirement for Age or Disability.......................................................................5.3
         Death..................................................................................................5.4

ARTICLE VI - EXERCISE OF OPTION

         Purchase of Stock......................................................................................6.1
         Accounting for Stock...................................................................................6.2
         Issuance of Shares.....................................................................................6.3
         Restriction on Shares..................................................................................6.4

ARTICLE VII - ADMINISTRATION

         Appointment, Term of Service & Removal.................................................................7.1
         Powers.................................................................................................7.2
         Quorum and Majority Action.............................................................................7.3
         Standard of Judicial Review of Committee Actions.......................................................7.4

ARTICLE VIII - ADOPTION OF PLAN BY OTHER EMPLOYER

         Adoption Procedure.....................................................................................8.1
         No Joint Venture Implied...............................................................................8.2

ARTICLE IX - TERMINATION AND AMENDMENT OF THE PLAN

         Termination............................................................................................9.1
         Amendment..............................................................................................9.2
</TABLE>


                                      -ii-

<PAGE>   4


<TABLE>
<CAPTION>
                                                                                                            SECTION

ARTICLE X - MISCELLANEOUS

<S>                                                                                                         <C>
         Designation of Beneficiary............................................................................10.1
         Plan Not An Employment Contract.......................................................................10.2
         All Participants' Rights are Equal....................................................................10.3
         Options Granted Are Not Transferable..................................................................10.4
         Voting of Stock.......................................................................................10.5
         No Stockholder Rights.................................................................................10.6
         Governmental Regulations..............................................................................10.7
         Notices...............................................................................................10.8
         Indemnification of Committee..........................................................................10.9
         Tax Withholding......................................................................................10.10
         Gender and Number....................................................................................10.11
         Severability.........................................................................................10.12
         Governing Law; Parties to Legal Actions..............................................................10.13
</TABLE>



                                      -iii-

<PAGE>   5

                                    ARTICLE I

                         PURPOSE, COMMITMENT AND INTENT


         1.1 PURPOSE. The purpose of this Plan is to provide Employees of the
Company and its Affiliates which adopt the Plan with an opportunity to purchase
Stock of the Company through offerings of options at a discount and thus develop
a stronger incentive to work for the continued success of the Company and its
Affiliates. Therefore, this Plan is available to all Employees of every Employer
upon their fulfilling the eligibility requirements of Section 3.1. Any Affiliate
may adopt it with the approval of the Committee by fulfilling the requirements
of Section 8.1. This Plan is sponsored by the Company.

         1.2 TERM OF PLAN. The Plan is effective June 1, 2000. No Option shall
be granted after May 31, 2010. The Plan shall remain in effect until all Options
under the Plan have been satisfied or expired.

         1.3 SHARE COMMITMENT. The aggregate number of Shares authorized to be
sold pursuant to Options granted under this Plan is 250,000 Shares, subject to
adjustment as provided in this Section. Any Shares relating to Options that are
granted, but subsequently lapse, are canceled, or are otherwise not exercised by
the final date for exercise, shall be available for future grants of Options.

         In the event of any stock dividend, split-up, recapitalization, merger,
consolidation, combination or exchange of Shares, or the like, as a result of
which shares shall be issued in respect of the outstanding Shares, or the Shares
shall be changed into the same or a different number of the same or another
class of stock, the total number of Shares authorized to be committed to this
Plan, the number of Shares subject to each outstanding Option and the Option
Price applicable to each Option shall be appropriately adjusted by the
Committee.

         1.4 INTENT. It is the intention of the Company to have the Plan qualify
as an "employee stock purchase plan" under section 423 of the Code. Therefore,
the provisions of the Plan are to be construed to govern participation in a
manner consistent with the requirements of section 423 of the Code.

         1.5 SHAREHOLDER APPROVAL. To be effective, this Plan must be approved
by the stockholders of each Employer within 12 months before or after the Plan
is approved by the board of directors of each Employer. The approval of
stockholders must comply with all applicable provisions of the corporate
charter, bylaws and applicable laws of the jurisdiction prescribing the method
and degree of stockholder approval required for the issuance of corporate stock
or options.



                                      I-1
<PAGE>   6

                                   ARTICLE II

                                   DEFINITIONS


         The words and phrases defined in this Article shall have the meaning
set out in these definitions throughout this Plan, unless the context in which
any word or phrase appears reasonably requires a broader, narrower, or different
meaning.

         2.1 "AFFILIATE" means any parent corporation and any subsidiary
corporation. The term "parent corporation" means any corporation (other than the
Company) in an unbroken chain of corporations ending with the Company if, at the
time of the action or transaction, each of the corporations other than the
Company owns stock possessing 50% or more of the total combined voting power of
all classes of stock in one of the other corporations in the chain. The term
"subsidiary corporation" means any corporation (other than the Company) in an
unbroken chain of corporations beginning with the Company if, at the time of the
granting of the Option, each of the corporations other than the last corporation
in the unbroken chain owns stock possessing 50% or more of the total combined
voting power of all classes of stock in one of the other corporations in the
chain.

         2.2 "BENEFICIARY" means the person who is entitled to receive amounts
under the Plan upon the death of a Participant.

         2.3 "BOARD OF DIRECTORS" means the board of directors of the Company.

         2.4 "CODE" means the Internal Revenue Code of 1986, as amended from
time to time.

         2.5 "COMMITTEE" means the committee appointed by the Board of Directors
of the Company to administer the Plan which shall be comprised solely of members
of the Board of Directors who qualify as non-employee directors as defined in
Rule 16b-3(b)(3) of the Securities Exchange Act of 1934, as amended.

         2.6 "COMPANY" means ILEX ONCOLOGY, INC., a Delaware corporation.

         2.7 "COMPENSATION" means the Employee's wages from the Company as
defined in section 3401(a) of the Code for purposes of Federal income tax
withholding at the source, reduced by all of the following items (even if
includable in gross income): bonuses, commissions, reimbursements or other
expense allowances, income from the exercise of a nonqualified stock option,
income resulting from a disqualifying disposition from an incentive stock option
or from this Plan, fringe benefits (cash and non-cash), moving expenses,
deferred compensation, and welfare benefits; and modified by including elective
contributions under a cafeteria plan described in section 125 of the Code and
elective contributions to any plan qualified under section 401(k) of the Code.


                                      II-1

<PAGE>   7

         2.8 "EMPLOYEE" means any person who is a common law employee of the
Employer excluding only those whose customary employment with the Employer is 20
hours or less per week.

         2.9 "EMPLOYER" means the Company and each Affiliate which has adopted
the Plan as provided in Section 8.1 of the Plan.

         2.10 "ENROLLMENT DATE" means the first day of each Offering Period.

         2.11 "EXERCISE DATE" means the last business day of the Purchase
Period.

         2.12 "FAIR MARKET VALUE" OR "FMV" of the Stock as of any date means the
average of the high and low sale prices of the Stock on that date (or if there
was no sale on a given date, the next preceding date on which there was a sale)
on the principal securities exchange on which the Stock is listed.

         2.13 "OFFERING PERIOD" means the twenty-four month period during which
an Option granted pursuant to the Plan may be exercised, commencing on the first
business day on or after July 1 and January 1 of each year and terminating on
the last business day in the periods ending twenty-four months later, provided
that the first Offering Period shall be a longer Offering Period of twenty-five
months, commencing on the first business on or after June 1, 2000 and ending
twenty- five months later on the last business day of the period ending June 30,
2002.

         2.14 "OPTION" means an option granted under this Plan to purchase
shares of Stock at the Option Price on the Exercise Date. Options shall not mean
either Incentive Options or Non-qualified Options granted under the ILEX
Oncology, Inc. 2000 Employee Stock Compensation Plan.

         2.15 "OPTION PRICE" means the price to be paid for each Share upon
exercise of an Option, which shall be the lesser of (a) 85% of the FMV of a
Share on the Enrollment Date or (b) 85% of the FMV of a Share on the Exercise
Date.

         2.16 "PARTICIPANT" means a person who is eligible to be granted an
Option under this Plan and who elects to have payroll deductions withheld under
the Plan for the purpose of exercising that Option on the Exercise Date.

         2.17 "PLAN" means the ILEX ONCOLOGY, INC. Employee Stock Purchase Plan,
as set out in this document and as it may be amended from time to time.

         2.18 "PURCHASE PERIOD" means the approximately six month period
commencing after one Exercise Date and ending on the next Exercise Date except
that the first Purchase Period of any Offering Period shall commence on the
Enrollment Date and end with the next Exercise Date, provided, however, that the
first Purchase Period of the first Offering Period under the Plan shall be
approximately seven months in duration.



                                      II-2
<PAGE>   8

         2.19 "SHARES" means shares of Stock.

         2.20 "STOCK" means the Company's common stock.





                                      II-3
<PAGE>   9

                                   ARTICLE III

                                   ELIGIBILITY


         3.1 GENERAL REQUIREMENTS. Each Employee is eligible to participate in
the Plan for a given Offering Period if he is an Employee on the Enrollment
Date, subject to the limitations imposed in Section 3.2.

         3.2 LIMITATIONS UPON PARTICIPATION. Any provision of this Plan to the
contrary notwithstanding, no Employee shall be granted an Option:

                  (a) if, immediately after the grant, the Employee would own,
         including all outstanding options which are still exercisable to
         purchase Stock, five percent (5%) or more of the total combined voting
         power or value of all classes of Stock of the Company or of any parent
         or subsidiary of the Company within the meaning of sections 423 and 424
         of the Code;

                  (b) which permits the Employee to purchase Stock under all
         employee stock purchase plans, as defined in section 423 of the Code,
         of the Company and all Affiliates at a rate which exceeds $25,000 in
         Fair Market Value of the Stock (determined at the time the Option is
         granted) for each calendar year in which the option granted to the
         Employee is outstanding at any time as provided in sections 423 and 424
         of the Code; or

                  (c) which permits the Employee rights to purchase Stock in
         excess of the number of Shares set by the Committee if it deems such a
         restriction to be appropriate.

                                      III-1

<PAGE>   10

                                   ARTICLE IV

                                  PARTICIPATION


         4.1 GRANT AND EXERCISE OF OPTION. Effective as of the Enrollment Date
of each Offering Period the Committee shall grant an Option to each Participant
participating in such Offering Period that shall be exercisable on each Exercise
Date during such Offering Period (at the applicable Option Price) only through
funds accumulated by the Employee through payroll deductions made prior to such
Exercise Date and retained in the Participant's Account as of such Exercise
Date. Provided, however, that in no event shall an Employee be permitted to
purchase during each Purchase Period more than a number of Shares determined by
dividing $12,500 by the FMV of a share of the Company's Stock on the Enrollment
Date. In addition, and notwithstanding the foregoing, to the extent necessary to
comply with section 423(b)(8) of the Code and to comply with the preceding
provisions of this Section 4.1, a Participant's payroll deductions may be
decreased to zero percent at such time during any Purchase Period which is
scheduled to end during the current calendar year (the "Current Purchase
Period") to the extent that the aggregate of all payroll deductions which were
previously used to purchase stock under the Plan in a prior Purchase Period
which ended during that calendar year plus all payroll deductions accumulated
with respect to the Current Purchase Period equal $21,250. Payroll deductions
shall recommence at the rate provided in such Participant's payroll deduction
agreement at the beginning of the first Purchase Period which is scheduled to
end in the following calendar year, unless terminate previously by the
Participant as provided herein.

         4.2 OFFERING PERIODS. The Plan shall be implemented by consecutive
overlapping Offering Periods with a new Offering Period commencing on the first
business on or after July 1 and January 1 of each year, or such other date at
the Board shall determine, and continuing thereafter until terminated in
accordance with Article IX hereunder. The Board shall have the power to change
the duration of Offering Periods with respect to future Offerings without
shareholder approval if such change is announced at least fifteen days prior the
scheduled beginning of the first Offering Period to be effected thereafter. In
addition, Employees may only participate in one Offering Period at any time.

         4.3 PAYROLL DEDUCTION. For an Employee to become eligible to receive an
Option granted for a given Offering Period, the Employee must complete a payroll
deduction form and file it with the Company no earlier than 30 nor later than 15
days prior to the beginning of the applicable Enrollment Date. The payroll
deduction form shall permit a Participant to elect to have withheld from his
Compensation an amount no less than one percent, nor more than fifteen percent,
of his Compensation (only in whole percentages) taken pro rata from the
Compensation paid to him by the Company. Each payroll deduction shall begin on
the first pay period ending after the applicable Enrollment Date and shall
continue through the last pay period in the Offering Period. No Participant
shall be permitted to begin payroll deductions at any other time. A Participant
may not make additional payments to his Plan account.


                                      IV-1

<PAGE>   11

         4.4 PAYROLL DEDUCTIONS CONTINUING. A Participant's election to have
payroll deductions shall remain in effect for all ensuing Offering Periods until
changed by the Participant by filing an appropriate amended payroll deduction
form not earlier than 30 nor later than 15 days prior to the applicable Offering
Period for which it is to be effective.

         4.5 RIGHT TO STOP OR ADJUST PAYROLL DEDUCTIONS. A Participant may
discontinue, payroll deductions and his participation in the Plan as provided in
Section 5.1. In addition, a Participant may increase or decrease his payroll
deductions during any Purchase Period by filing an amended payroll deduction
form at least 15 days prior to the effective date of the change.

         4.6 ACCOUNTING FOR FUNDS. As of each payroll deduction period the
Employer shall cause to be credited to the Participant's payroll deduction
account in a ledger established for that purpose the funds withheld from and
attributable to the Employee's compensation for that period. No interest shall
be credited to the Participant's payroll deduction account at any time. The
obligation of the Employer to the Participant for this account shall be a
general corporate obligation and shall not be funded through a trust nor secured
by any assets which would cause the Participant to be other than a general
creditor of the Employer.

         4.7 EMPLOYER'S USE OF FUNDS. All payroll deductions received or held by
an Employer may be used by the Employer for any corporate purposes and the
Employer shall not be obligated to segregate such payroll deductions.



                                      IV-2

<PAGE>   12

                                    ARTICLE V

                             IN SERVICE WITHDRAWAL,
                           TERMINATION OF EMPLOYMENT,
                               RETIREMENT OR DEATH


         5.1 IN SERVICE WITHDRAWAL. A Participant may, at any time on or before
15 days prior to an Exercise Date, or such other date as shall be determined by
the Committee from time to time, elect to withdraw all funds then credited to
his payroll deduction account by giving written notice to his Employer in
accordance with the rules established by the Committee. All funds credited to
the Participant's payroll deduction account shall be paid to him as soon as
administratively feasible. The withdrawal election terminates the Participant's
right to exercise his Option on the Exercise Date and his entitlement to elect
any further payroll deductions for the then current and immediately following
Purchase Period. Should the Participant wish to participate in any given future
Purchase Period within the existing Offering Period, the Participant must file a
new payroll deduction election no earlier than 3 nor later than 15 days prior to
the beginning of the applicable Purchase Period within the Offering Period.

         5.2 TERMINATION OF EMPLOYMENT. If a Participant's employment is
terminated for any reason other than retirement for age or disability as
described in Section 5.3, prior to the Exercise Date, the Option granted to the
Participant for that Offering Period shall lapse. The Participant's payroll
deduction account shall be returned to him as soon as administratively feasible.

         5.3 RETIREMENT FOR AGE OR DISABILITY. If a Participant retires for age
or disability under the then established rules of the Company, his Exercise Date
shall be the last day of the month prior to his retirement for age or
disability. At that time his Option shall be exercised in accordance with the
terms of the Plan. Then any funds remaining in his payroll deduction account
shall be returned to him as soon as administratively feasible.

         5.4 DEATH. If a Participant dies before an Exercise Date, the Option
granted to the Participant for that Offering Period shall lapse. The
Participant's payroll deduction account shall be returned to him as soon as
administratively feasible. If the Participant dies after an Exercise Date but
prior to the delivery of his certificate, the Stock shall be delivered to his
Beneficiary (or to his estate if he has no Beneficiary). If there is no
Beneficiary, the Stock shall be held in the Participant's account until the
representative of the estate has been appointed and provides such evidence as
may be required by the Committee before the certificate is delivered to the
proper party together with a check in the amount of any remaining funds in the
Participant's payroll deduction account.


                                       V-1

<PAGE>   13

                                   ARTICLE VI

                               EXERCISE OF OPTION


         6.1 PURCHASE OF STOCK. Subject to the limitations in Section 3.2 of the
Plan, on the Exercise Date of each Purchase Period each Participant's payroll
deduction account shall be used to purchase the maximum number of whole shares
of Stock that can be purchased at the Option Price for that Purchase Period. Any
funds remaining in a Participant's payroll deduction account after the exercise
of his Option for any Purchase Period shall remain in the Participant's account
to be used in the ensuing Purchase Period, together with new payroll deductions,
if any, for that Purchase Period to exercise the next succeeding Option which is
to be exercised. If in any Purchase Period the total number of shares of Stock
to be purchased by all Participants exceed the number of shares of Stock
committed to the Plan, then each Participant shall be entitled to purchase only
his pro rata portion of the shares of Stock remaining available under the Plan
based on the balances in each Participant's payroll deduction account as of the
Exercise Date. No fractional shares of Stock may be purchased under this Plan.
After the purchase of all shares of Stock available on Exercise Date, all
Options granted for the Purchase Period to the extent not used shall terminate.

         6.2 ACCOUNTING FOR STOCK. After each Exercise Date of each Purchase
Period, a report shall be given to each Participant stating the amount of his
payroll deduction account, the number of shares of Stock purchased and the
applicable Option Price.

         6.3 ISSUANCE OF SHARES. As soon as administratively feasible after the
end of the Purchase Period the Committee shall advise the appropriate officer of
the Company that the terms of the Plan have been complied with and that it is
appropriate for the officer to cause to be issued the shares of Stock upon which
Options have been exercised under the Plan. The Committee may determine in its
discretion the manner of delivery of the shares of Stock purchased under the
Plan, which may be by electronic account entry into new or existing accounts,
delivery of certificates or any other means as the Committee, in its discretion,
deems appropriate. The Committee may, in its discretion, hold the certificate
for any shares of Stock or cause it to be legended in order to comply with the
securities laws of the applicable jurisdiction.

         6.4 RESTRICTION ON SHARES. A Participant shall be free to undertake a
disposition (as that term is defined in Section 424(c) of the Code) of the
shares in his account at any time, whether by sale, exchange, gift, or other
transfer of legal title, but in the absence of such a disposition of the shares,
the shares must remain in the Participant's account at the brokerage or other
financial services firm designated by the Committee until the holding period set
forth in Section 423(a) of the Code has been satisfied. With respect to Shares
for which such holding period has been satisfied, the Participant may direct
that those Shares be moved to another account of Participant's choosing or
request that a stock certificate be issued and delivered to him.


                                      VI-1

<PAGE>   14

         Notwithstanding anything to the contrary contained in this Plan, a
Participant shall not transfer or otherwise dispose of Stock in violation of the
Company's Insider Trading Policy.



                                      VI-2

<PAGE>   15

                                   ARTICLE VII

                                 ADMINISTRATION


         7.1 APPOINTMENT, TERM OF SERVICE & REMOVAL. The Board of Directors
shall appoint a Committee to administer this Plan. The members shall serve until
their resignation, death or removal. Any member may resign at any time by
mailing a written resignation to the Board of Directors. Any member may be
removed by the Board of Directors, with or without cause. Vacancies may be
filled by the Board of Directors from time to time.

         7.2 POWERS. The Committee has the exclusive responsibility for the
general administration of the Plan, and has all powers necessary to accomplish
that purpose, including but not limited to the following rights, powers, and
authorities:

                  (a) to make rules for administering the Plan so long as they
         are not inconsistent with the terms of the Plan;

                  (b) to construe all provisions of the Plan;

                  (c) to correct any defect, supply any omission, or reconcile
         any inconsistency which may appear in the Plan;

                  (d) to select, employ, and compensate at any time any
         consultants, accountants, attorneys, and other agents the Committee
         believes necessary or advisable for the proper administration of the
         Plan;

                  (e) to determine all questions relating to eligibility, Fair
         Market Value, Option Price and all other matters relating to benefits
         or Participants' entitlement to benefits;

                  (f) to determine all controversies relating to the
         administration of the Plan, including but not limited to any
         differences of opinion arising between the Company and a Participant,
         and any questions it believes advisable for the proper administration
         of the Plan; and

                  (g) to delegate any clerical or recordation duties of the
         Committee as the Committee believes is advisable to properly administer
         the Plan.

         7.3 QUORUM AND MAJORITY ACTION. A majority of the Committee constitutes
a quorum for the transaction of business. The vote of a majority of the members
present at any meeting shall decide any question brought before that meeting. In
addition, the Committee may decide any


                                      VII-1

<PAGE>   16

question by a vote, taken without a meeting, of a majority of its members via
telephone, computer, fax or any other media of communication.

         7.4 STANDARD OF JUDICIAL REVIEW OF COMMITTEE ACTIONS. The Committee has
full and absolute discretion in the exercise of each and every aspect of its
authority under the Plan. Notwithstanding anything to the contrary, any action
taken, or ruling or decision made, by the Committee in the exercise of any of
its powers and authorities under the Plan shall be final and conclusive as to
all parties other than the Company, including without limitation all
Participants and their Beneficiaries, regardless of whether the Committee or one
or more of its members may have an actual or potential conflict of interest with
respect to the subject matter of the action, ruling, or decision. No final
action, ruling, or decision of the Committee shall be subject to de novo review
in any judicial proceeding; and no final action, ruling, or decision of the
Committee may be set aside unless it is held to have been arbitrary and
capricious by a final judgment of a court having jurisdiction with respect to
the issue.



                                      VII-2

<PAGE>   17

                                  ARTICLE VIII

                       ADOPTION OF PLAN BY OTHER EMPLOYERS


         8.1 ADOPTION PROCEDURE. With the approval of the Committee, any
Affiliate may adopt this Plan by:

                  (a) a certified resolution or consent of the board of
         directors of the adopting Affiliate or an executed adoption instrument
         (approved by the board of directors of the adopting Affiliate) agreeing
         to be bound as an Affiliate by all the terms, conditions and
         limitations of this Plan; and

                  (b) providing all information required by the Committee.

         8.2 NO JOINT VENTURE IMPLIED. The document which evidences the adoption
of the Plan by an Affiliate shall become a part of this Plan. However, neither
the adoption of this Plan by an Affiliate nor any act performed by it in
relation to this Plan shall create a joint venture or partnership relation
between it and the Company or any other Affiliate.



                                     VIII-1

<PAGE>   18

                                   ARTICLE IX

                      TERMINATION AND AMENDMENT OF THE PLAN


         9.1 TERMINATION. The Company may, by action of the Board of Directors,
terminate the Plan at any time and for any reason. The Plan shall automatically
terminate upon the purchase by Participants of all shares of Stock committed to
the Plan, unless the number of Shares committed to the Plan are increased by the
Board of Directors and approved by the shareholders of the Company. Upon
termination of the Plan, as soon as administratively feasible there shall be
refunded to each Participant the remaining funds in his payroll deduction
account, and there shall be forwarded to the Participants certificates for all
shares of Stock held under the Plan for the account of Participants. The
termination of this Plan shall not affect the current Options already
outstanding under the Plan to the extent there are Shares committed, unless the
Participants agree.

         9.2 AMENDMENT. The Board of Directors reserves the right to modify,
alter or amend the Plan at any time and from time to time to any extent that it
deems advisable, including, without limiting the generality of the foregoing,
any amendment deemed necessary to ensure compliance of the Plan with Section 423
of the Code. The Board of Directors may suspend operation of the Plan for any
period as it may deem advisable. However, no amendment or suspension shall
operate to reduce any amounts previously allocated to a Participant's payroll
deduction account, to reduce a Participant's rights with respect to shares of
Stock previously purchased and held on his behalf under the Plan nor to affect
the current Option a Participant already has outstanding under the Plan without
the Participant's agreement. Any amendment changing the aggregate number of
Shares to be committed to the Plan or the class of employees eligible to receive
Options under the Plan must have stockholder approval as set forth in Section
1.4.



                                      IX-1

<PAGE>   19

                                    ARTICLE X

                                  MISCELLANEOUS


         10.1 DESIGNATION OF BENEFICIARY.

                           (a) A Participant may file a written or electronic
                  designation (as permitted by the Committee) of a Beneficiary
                  who is to receive any cash and Shares credited to the
                  Participant's account under the Plan.

                           (b) A Participant may change his designation of a
                  Beneficiary at any time by written notice. If a Participant
                  dies when he has not validly designated a Beneficiary under
                  the Plan, the Company shall deliver such Shares and cash to
                  the executor or administrator of the estate of the
                  Participant, or if no such executor or administrator has been
                  appointed (to the knowledge of the Company), the Company, in
                  its discretion, may deliver such Shares and cash to the spouse
                  or to any one or more dependents or relatives of the
                  Participant, or if no spouse, dependent or relative is known
                  to the Company, then to such other person as the Company may
                  designate.

         10.2 PLAN NOT AN EMPLOYMENT CONTRACT. The adoption and maintenance of
this Plan is not a contract between the Company and its Employees which gives
any Employee the right to be retained in its employment. Likewise, it is not
intended to interfere with the rights of the Company to discharge any Employee
at any time or to interfere with the Employee's right to terminate his
employment at any time.

         10.3 ALL PARTICIPANTS' RIGHTS ARE EQUAL. All Participants will have the
same rights and privileges under this Plan as are required by section 423 of the
Code and section 1.423-2(f) of the regulations promulgated under that section of
the Code.

         10.4 OPTIONS GRANTED ARE NOT TRANSFERABLE. No Option granted a
Participant under this Plan is transferable by the Participant and must be
exercisable only by him. In the event any Participant attempts to violate the
terms of this Section, any Option held by the Participant shall be terminated by
the Company and upon return to the Participant of the remaining funds in his
payroll deduction account, all of his rights under the Plan will terminate.

         10.5 VOTING OF STOCK. Shares of Stock held under the Plan for the
account of each Participant shall be voted by the holder of record of those
shares in accordance with the Participant's instructions.



                                       X-1

<PAGE>   20

         10.6 NO STOCKHOLDER RIGHTS. No eligible Employee or Participant shall
by reason of participation in the Plan have any rights of a stockholder of the
Company until he acquires shares of Stock as provided in this Plan.

         10.7 GOVERNMENTAL REGULATIONS. The obligation to sell or deliver the
shares of Stock under this Plan is subject to the approval of all governmental
authorities required in connection with the authorization, purchase, issuance or
sale of that Stock.

         10.8 NOTICES. All notices and other communication in connection with
the Plan shall be in the form specified by the Committee and shall be deemed to
have been duly given when sent to the Participant at his last known address or
to his designated personal representative or beneficiary, or to the Company or
its designated representative, as the case may be.

         10.9 INDEMNIFICATION OF COMMITTEE. In addition to all other rights of
indemnification as they may have as directors or as members of the Committee,
the members of the Committee shall be indemnified by the Company against the
reasonable expenses, including attorneys' fees, actually and necessarily
incurred in connection with the defense of any action, suit or proceeding, or in
connection with any appeal, to which they or any of them may be a party by
reason of any action taken or failure to act under or in connection with the
Plan or any Option granted under the Plan, and against all amounts paid in
settlement (provided the settlement is approved by independent legal counsel
selected by the Company) or paid by them in satisfaction of a judgment in any
action, suit or proceeding, except in relation to matters as to which it is
adjudged in the action, suit or proceeding, that the Committee member is liable
for gross negligence or willful misconduct in the performance of his duties.

         10.10 TAX WITHHOLDING. At the time a Participant's Option is exercised
or at the time a Participant disposes of some or all of the Stock purchased
under the Plan, the Participant must make adequate provision for the Employer's
federal, state or other tax withholding obligations, if any, which arise upon
the exercise of the Option or the disposition of the Stock. At any time, the
Employer may, but shall not be obligated to, withhold from the Participant's
compensation the amount necessary for the Employer to meet applicable
withholding obligations.

         10.11 GENDER AND NUMBER. If the context requires it, words of one
gender when used in this Plan shall include the other genders, and words used in
the singular or plural shall include the other.

         10.12 SEVERABILITY. Each provision of this Plan may be severed. If any
provision is determined to be invalid or unenforceable, that determination shall
not affect the validity or enforceability of any other provision.

         10.13 GOVERNING LAW; PARTIES TO LEGAL ACTIONS. The provisions of this
Plan shall be construed, administered, and governed under the laws of the State
of Texas and, to the extent



                                       X-2

<PAGE>   21


applicable, by the securities, tax, employment and other laws of the United
States which are applicable to an employee stock purchase plan.



                                       X-3