Document:

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                                                                   EXHIBIT 10.19

                           CHANGE IN CONTROL AGREEMENT

         THIS AGREEMENT between UroCor, Inc., a Delaware corporation (the
"Company"), and _______________________________________ (the "Employee") is
effective as of this ____ day of ______, 19__ (the "Effective Date"). Certain
capitalized terms used herein are defined in Section 21.

                                W I T N E S S E T H:

         WHEREAS, the Company considers it to be in the best interests of its
stockholders to encourage the continued employment of certain key employees
of the Company notwithstanding the possibility, threat or occurrence of a
Change in Control of the Company; and

         WHEREAS, the Employee is a key employee of the Company; and

         WHEREAS, the Company believes that the possibility of the occurrence
of a Change in Control of the Company may result in the termination by the
Employee of the Employee's employment by the Company or in the distraction of
the Employee from the performance of his duties to the Company, in either
case to the detriment of the Company and its stockholders; and

         WHEREAS, the Company recognizes that the Employee could suffer
adverse financial and professional consequences if a Change in Control of the
Company were to occur; and

         WHEREAS, the Company wishes to enter into this Agreement to protect
the Employee if a Change in Control of the Company occurs, thereby
encouraging the Employee to remain in the employ of the Company and not to be
distracted from the performance of his duties to the Company by the
possibility of a Change in Control of the Company;

         NOW, THEREFORE, the parties agree as follows:

         SECTION 1.        OTHER EMPLOYMENT ARRANGEMENTS.

         (a) This Agreement does not affect the Employee's existing or future
employment arrangements with the Company unless a Change in Control of the
Company shall have occurred before the expiration of the term of this
Agreement. The Employee's employment with the Company shall continue to be
governed by the Employee's existing or future employment agreements with the
Company, if any, or, in the absence of any employment agreement, shall
continue to be at the will of the Board of Directors or, if the Employee is
not an officer of the Company at the time of the termination of the
Employee's employment with the Company, the will of the Chief Executive
Officer of the Company, except that if (i) a Change in Control of the Company
shall have occurred before the expiration of the term of this Agreement and
(ii) the Employee's employment with the Company is terminated (whether by the
Employee or the Company or automatically as provided in Section 3) after the
occurrence of that Change in Control of the Company, then the Employee shall
be entitled to receive certain benefits as provided in this Agreement.

         (b) Notwithstanding anything contained in this Agreement to the
contrary, if following the commencement of any discussions with any person
that ultimately results in a Change in Control of the Company, (i) the
Employee's employment with the Company is terminated, (ii) the Employee is
removed from any material duties or position with the Company, (iii) the
Employee's Base Salary is reduced or (iv) the Employee's annual bonus is
reduced to an amount less than the Benchmark Bonus, then for all purposes of
this Agreement, such Change in Control of the Company shall be deemed to have
occurred on the date immediately prior to the date of such termination,
removal or reduction.

         (c) Nothing in this Agreement shall prevent or limit the Employee's
continuing or future participation in any plan, program, policy or practice
of or provided by the Company or any of its Affiliates and for which the
Employee may qualify, nor shall anything herein limit or otherwise affect
such rights as the Employee may have under any contract or agreement with the
Company or any of its Affiliates. Amounts which are vested benefits or which
the Employee is otherwise entitled to receive under any plan, program, policy
or practice of or provided by, or any contract or agreement with, the Company
or any of its Affiliates at or subsequent to the date of termination of
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the Employee's employment with the Company shall be payable or otherwise
provided in accordance with such plan, program, policy or practice or
contract or agreement except as explicitly modified by this Agreement.

         SECTION 2. CHANGE IN CONTROL OF THE COMPANY. A "Change in Control of
the Company" shall have occurred if, after the Effective Date:

                  (i) a report on Schedule 13D or Schedule 14D-1 (or any
         successor schedule, form or report) shall be filed with the Commission
         pursuant to the Exchange Act and that report discloses that any person
         (within the meaning of Section 13(d) or Section 14(d)(2) of the
         Exchange Act), other than the Company (or one of its subsidiaries) or
         any employee benefit plan sponsored by the Company (or one of its
         subsidiaries), is the beneficial owner (as that term is defined in Rule
         13d-3 or any successor rule or regulation promulgated under the
         Exchange Act), directly or indirectly, of 20 percent or more of the
         outstanding Voting Stock;

                  (ii) any person (within the meaning of Section 13(d) or
         Section 14(d)(2) of the Exchange Act), other than the Company (or one
         of its subsidiaries) or any employee benefit plan sponsored by the
         Company (or one of its subsidiaries), shall purchase securities
         pursuant to a tender offer or exchange offer to acquire any Voting
         Stock (or any securities convertible into Voting Stock) and,
         immediately after consummation of that purchase, that person is the
         beneficial owner (as that term is defined in Rule 13d-3 or any
         successor rule or regulation promulgated under the Exchange Act),
         directly or indirectly, of 20 percent or more of the outstanding Voting
         Stock (such person's beneficial ownership to be determined, in the case
         of rights to acquire Voting Stock, pursuant to paragraph (d) of Rule
         13d-3 or any successor rule or regulation promulgated under the
         Exchange Act);

                  (iii) the consummation of:

                                    (x) a merger, stock exchange, consolidation
                           or reorganization of the Company with or into any
                           other person if as a result of such merger, stock
                           exchange, consolidation or reorganization, 50 percent
                           or less of the combined voting power of the
                           then-outstanding securities of such other person
                           immediately after such merger, stock exchange,
                           consolidation or reorganization are held in the
                           aggregate by the holders of Voting Stock immediately
                           prior to such merger, consolidation or
                           reorganization;

                                    (y) any sale, lease, exchange or other
                           transfer of all or substantially all the assets of
                           the Company and its consolidated subsidiaries to any
                           other person if as a result of such sale, lease,
                           exchange or other transfer, 50 percent or less of the
                           combined voting power of the then-outstanding
                           securities of such other person immediately after
                           such sale, lease, exchange or other transfer are held
                           in the aggregate by the holders of Voting Stock
                           immediately prior to such sale, lease, exchange or
                           other transfer; or

                                    (z) a transaction immediately after the
                           consummation of which any person (within the meaning
                           of Section 13(d) or Section 14(d)(2) of the Exchange
                           Act) would be the beneficial owner (as that term is
                           defined in Rule 13d-3 or any successor rule or
                           regulation promulgated under the Exchange Act),
                           directly or indirectly, of more than 50 percent of
                           the outstanding Voting Stock;

                  (iv) the stockholders of the Company approve the dissolution
         of the Company; or

                  (v) during any period of 12 consecutive months, the
         individuals who at the beginning of that period constituted the Board
         of Directors shall cease to constitute a majority of the Board of
         Directors, unless the election, or the nomination for election by the
         Company's stockholders, of each director of the Company first elected
         during such period was approved by a vote of at least a two-thirds of
         the directors of the Company then still in office who were directors of
         the Company at the beginning of any such period.

         SECTION 3. TERM OF THIS AGREEMENT. The term of this Agreement shall
begin on the Effective Date and shall expire on the first to occur of:
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                  (i)  the Employee's death, the Employee's Disability or the
         Employee's Retirement, which events shall also be deemed automatically
         to terminate the Employee's employment by the Company; or

                  (ii) the termination by the Employee or the Company of the
         Employee's employment by the Company.

The expiration of the term of this Agreement shall not terminate this
Agreement itself or affect the right of the Employee or the Employee's legal
representatives to enforce the payment of any amount or other benefit to
which the Employee was entitled before the expiration of the term of this
Agreement or to which the Employee became entitled as a result of the event
(including the termination, whether by the Employee or the Company or
automatically as provided in this Section 3, of the Employee's employment by
the Company) that caused the term of this Agreement to expire.

               SECTION 4.  EVENT OF TERMINATION FOR CAUSE. An "Event of
Termination for Cause" shall have occurred if, after a Change in Control of
the Company, the Employee shall have committed:

                  (i)      gross negligence or willful  misconduct in connection
         with his duties or in the course of his employment with the Company;

                  (ii)     an act of fraud, embezzlement or theft in connection
         with his duties or in the course of his employment with the Company;

                  (iii)    intentional wrongful damage to property of the
         Company;

                  (iv)     intentional wrongful disclosure of secret processes
         or confidential information of the Company; or

                  (v)      an act leading to a conviction of a felony or a
         misdemeanor involving moral turpitude.

For purposes of this Agreement, no act, or failure to act, on the part of the
Employee shall be deemed "intentional" if it was due primarily to an error in
judgment or negligence, but shall be deemed "intentional" only if done, or
omitted to be done, by the Employee not in good faith and without reasonable
belief that his action or omission was in the best interest of the Company.
Notwithstanding the foregoing, the Employee shall not be deemed to have been
terminated as a result of an "Event of Termination for Cause" hereunder
unless and until there shall have been delivered to the Employee a copy of a
resolution duly adopted by the affirmative vote of not less than
three-quarters of the Board of Directors then in office at a meeting of the
Board of Directors called and held for such purpose (after reasonable notice
to the Employee and an opportunity for the Employee, together with his
counsel, to be heard before the Board of Directors), finding that, in the
good faith opinion of the Board of Directors, the Employee had committed an
act set forth above in this Section 4 and specifying the particulars thereof
in detail. Nothing herein shall limit the right of the Employee or his legal
representatives to contest the validity or propriety of any such
determination.

     SECTION 5. AN EVENT OF TERMINATION FOR GOOD REASON. An "Event of
Termination for Good Reason" shall have occurred if, after a Change in
Control of the Company, the Company shall:

                  (i) assign to the Employee any duties inconsistent with the
         Employee's position (including offices, titles and reporting
         requirements), authority, duties or responsibilities with the Company
         in effect immediately before the occurrence of the first Change in
         Control of the Company or otherwise make any change in any such
         position, authority, duties or responsibilities;

                  (ii) remove the Employee from, or fail to re-elect or appoint
         the Employee to, any duties or position with the Company or any of its
         Affiliates that were assigned or held by the Employee immediately
         before the occurrence of the first Change in Control of the Company,
         except that a nominal change in the Employee's title that is merely
         descriptive and does not affect rank or status shall not constitute
         such an event;
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                  (iii) take any other action that results in a material
         diminution in such position, authority, duties or responsibilities or
         otherwise take any action that materially interferes therewith;

                  (iv) reduce the Employee's annual base salary as in effect
         immediately before the occurrence of the first Change in Control of the
         Company or as the Employee's annual base salary may be increased from
         time to time after that occurrence (the "Base Salary");

                  (v) reduce the Employee's annual bonus to an amount less than
         ___% of the Employee's Base Salary (the "Benchmark Bonus");

                  (vi) relocate the Employee's principal office outside of the
         metropolitan area of Oklahoma City, Oklahoma;

                  (vii) fail to (x) continue in effect any bonus, incentive,
         profit sharing, performance, savings, retirement or pension policy,
         plan, program or arrangement (such policies, plans, programs and
         arrangements collectively being referred to herein as "Basic Benefit
         Plans"), including, but not limited to, any deferred compensation,
         supplemental executive retirement or other retirement income, stock
         option, stock purchase, stock appreciation, or similar policy, plan,
         program or arrangement of the Company, in which the Employee was a
         participant immediately before the occurrence of the first Change in
         Control of the Company, or any substitute plan adopted by the Board of
         Directors and in which the Employee was a participant immediately
         before the occurrence of the last Change in Control of the Company,
         unless an equitable and reasonably comparable arrangement (embodied in
         a substitute or alternative benefit or plan) shall have been made with
         respect to such Basic Benefit Plan promptly following the occurrence of
         the last Change in Control of the Company, or (y) continue the
         Employee's participation in any Basic Benefit Plan (or any substitute
         or alternative plan) on substantially the same basis, both in terms of
         the amount of benefits provided to the Employee (which are in any event
         always subject to the terms of any applicable Basic Benefit Plan) and
         the level of the Employee's participation relative to other
         participants, as existed immediately before the occurrence of the first
         Change in Control of the Company;

                  (viii) fail to continue to provide the Employee with benefits
         substantially similar to those enjoyed by the Employee under any of the
         Company's other employee benefit plans, policies, programs and
         arrangements (the "Other Benefit Plans"), including, but not limited
         to, life insurance, medical, dental, health, hospital, accident or
         disability plans, in which the Employee was a participant immediately
         before the occurrence of the first Change in Control of the Company;

                  (ix) take any action that would directly or indirectly
         materially reduce any other non-contractual benefits that were provided
         to the Employee by the Company immediately before the occurrence of the
         first Change in Control of the Company or deprive the Employee of any
         material fringe benefit enjoyed by the Employee immediately before the
         occurrence of the first Change in Control of the Company;

                  (x) fail to provide the Employee with the number of paid
         vacation days to which the Employee was entitled in accordance with the
         Company's vacation policy in effect immediately before the occurrence
         of the first Change in Control of the Company;

                  (xi) fail to continue to provide Employee with office space,
         related facilities and support personnel (including, but not limited
         to, administrative and secretarial assistance) (y) that are both
         commensurate with Employee's responsibilities to and position with the
         Company immediately before the occurrence of the first Change in
         Control of the Company and not materially dissimilar to the office
         space, related facilities and support personnel provided to other
         employees of the Company having comparable responsibility to the
         Employee, or (z) that are physically located at the Company's principal
         executive offices;

                  (xii) require the Employee to perform a majority of his duties
         outside the Company's principal executive offices for a period of more
         than 21 consecutive days or for more than 90 days in any calendar year;
<PAGE>

                  (xiii) fail to honor any provision of any employment agreement
         Employee has or may in the future have with the Company or fail to
         honor any provision of this Agreement;

                  (xiv) give effective notice of an election to terminate at the
         end of the term or extended the term of any employment agreement
         Employee has or may in the future have with the Company in accordance
         with the terms of any such agreement; or

                  (xv) purport to terminate the Employee's employment by the
         Company unless notice of that termination shall have been given to the
         Employee pursuant to, and that notice shall meet the requirements of,
         Section 6.

         SECTION 6. NOTICE OF TERMINATION. If a Change in Control of the
Company shall have occurred before the expiration of the term of this
Agreement, any subsequent termination by the Employee or the Company of the
Employee's employment by the Company, or any determination of the Employee's
Disability, shall be communicated by notice to the other party that shall
indicate the specific paragraph of Section 7 pursuant to which the Employee
is to receive benefits as a result of the termination. If the notice states
that the Employee's employment by the Company has been automatically
terminated as a result of the Employee's Disability, the notice shall (i)
specifically describe the basis for the determination of the Employee's
Disability, and (ii) state the date of the determination of the Employee's
Disability, which date shall be not more than ten (10) days before the date
such notice is given. If the notice is from the Company and states that the
Employee's employment by the Company is terminated by the Company as a result
of the occurrence of an Event of Termination for Cause, the notice shall
specifically describe the action or inaction of the Employee that the Company
believes constitutes an Event of Termination for Cause and shall be
accompanied by a copy of the resolution satisfying Section 4. If the notice
is from the Employee and states that the Employee's employment by the Company
is terminated by the Employee as a result of the occurrence of an Event of
Termination for Good Reason, the notice shall specifically describe the
action or inaction of the Company that the Employee believes constitutes an
Event of Termination for Good Reason. Each notice given pursuant to this
Section 6 (other than a notice stating that the Employee's employment by the
Company has been automatically terminated as a result of the Employee's
Disability) shall state a date, which shall be not fewer than thirty (30)
days nor more than sixty (60) days after the date such notice is given, on
which the termination of the Employee's employment by the Company is
effective. The date so stated in accordance with this Section 6 shall be the
"Termination Date". If a Change in Control of the Company shall have occurred
before the expiration of the term of this Agreement, any subsequent purported
termination by the Company of the Employee's employment by the Company, or
any subsequent purported determination by the Company of the Employee's
Disability, shall be ineffective unless that termination or determination
shall have been communicated by the Company to the Employee by notice that
meets the requirements of the foregoing provisions of this Section 6 and the
provisions of Section 9.

         SECTION 7. BENEFITS PAYABLE ON CHANGE IN CONTROL AND TERMINATION.
(a) If (x) a Change in Control of the Company shall have occurred before the
expiration of the term of this Agreement, and (y) the Employee's employment
by the Company is terminated (whether by the Employee or the Company or
automatically as provided in Section 3) after the occurrence of that Change
in Control of the Company, the Employee shall be entitled to the following
benefits:

                  (i) If the Employee's employment by the Company is terminated
         (x) by the Company as a result of the occurrence of an Event of
         Termination for Cause, or (y) by the Employee before the occurrence of
         an Event of Termination for Good Reason, then the Company shall pay to
         the Employee the Base Salary accrued through the Termination Date but
         not previously paid to the Employee, and the Employee shall be entitled
         to any other amounts or benefits provided under any plan, policy,
         practice, program, contract or arrangement of or with the Company,
         including, but not limited to, the Basic Benefit Plans and the Other
         Benefit Plans, which shall be governed by the terms thereof (except as
         explicitly modified by this Agreement).

                  (ii) If the Employee's employment by the Company is
         automatically terminated as a result of the Employee's death, the
         Employee's Disability or the Employee's Retirement, then (x) the
         Company shall pay to the Employee the Base Salary accrued through the
         date of the occurrence of that event but not previously paid to the
         Employee, and (y) the Employee shall be entitled to any other amounts
         or benefits provided under any plan, policy, practice, program,
         contract or arrangement of or with the Company, including, but not
         limited to, the Basic Benefit
<PAGE>

         Plans and the Other Benefit Plans, which shall be governed by the terms
         thereof (except as explicitly modified by this Agreement).

                  (iii) If the Employee's employment by the Company is
         terminated (x) by the Company otherwise than as a result of the
         occurrence of an Event of Termination for Cause, or (y) by the Employee
         after the occurrence of an Event of Termination for Good Reason, then
         the Employee shall be entitled to the following:

                           (1) the Company shall pay to the Employee the Base
                  Salary and compensation for earned but unused vacation time
                  accrued through the Termination Date but not previously paid
                  to the Employee;

                           (2) the Company shall pay to the Employee an amount
                  equal to the product of (A) the highest aggregate annual
                  bonus, incentive or other payment of cash compensation in
                  addition to annual base salary pursuant to any bonus,
                  incentive, profit-sharing, performance, discretionary pay or
                  similar policy, plan, program or arrangement of the Company
                  ("Incentive Pay") paid or payable to the Executive (including
                  any deferred portion thereof) for any fiscal year (or portion
                  thereof) of the Company ending after the Effective Date (the
                  "Highest Bonus"), and (B) a fraction, the numerator of which
                  is the number of days in the current fiscal year of the
                  Company through the Date of Termination and the denominator of
                  which is 365;

                           (3) the Company shall pay to the Employee, as a lump
                  sum, an amount (the "Severance Payment") equal to one and
                  one-half (1 1/2) times the sum of:

                                    (A) the amount (including any deferred
                           portion thereof) of the Base Salary that would have
                           been paid to the Employee during the fiscal year of
                           the Company in which the Termination Date occurs
                           based on the assumption that the Employee's
                           employment by the Company had continued throughout
                           that fiscal year at the Base Salary at the highest
                           rate in effect at any time during the term of this
                           Agreement; plus

                                    (B)  the amount of the Highest Bonus;

                          (4)  the Company (at its sole expense) shall take the
                  following actions:

                                    (A) throughout the Relevant Period, the
                           Company shall maintain in effect, and not materially
                           reduce the benefits provided by, each of the Other
                           Benefit Plans in which the Employee was a participant
                           immediately before the Termination Date; and

                                    (B) the Company shall arrange for the
                           Employee's uninterrupted participation throughout the
                           Relevant Period in each of such Other Benefit Plans,

                  PROVIDED that if the Employee's participation after the
                  Termination Date in any such Other Benefit Plan is not
                  permitted by the terms of that Other Benefit Plan, then
                  throughout the Relevant Period, the Company (at its sole
                  expense) shall provide the Employee with substantially the
                  same benefits that were provided to the Employee by that Other
                  Benefit Plan immediately before the Termination Date; and

                           (5) the Employee shall be entitled to any other
                  amounts or benefits provided under any plan, policy, practice,
                  program, contract or
<PAGE>

                  arrangement of or with the Company, including, but not limited
                  to, the Basic Benefit Plans and the Other Benefit Plans, which
                  shall be governed by the terms thereof (except as explicitly
                  modified by this Agreement).

         (b) Each payment required to be made to the Employee pursuant to the
foregoing provisions of this Section 7(a) above (i) shall be made by check
drawn on an account of the Company at a bank located in the United States of
America, and (ii) shall be paid (x) if the Employee's employment by the
Company was terminated as a result of the Employee's death, the Employee's
Disability or the Employee's Retirement, not more than thirty (30) days
immediately following the date of the occurrence of that event, and (y) if
the Employee's employment by the Company was terminated for any other reason,
not more than ten (10) days immediately following the Termination Date.

         SECTION 8.        SUCCESSORS.  If a Change in Control of the Company
shall have occurred before the expiration of the term of this Agreement,

                  (i) the Company shall not, directly or indirectly, consolidate
         with, merge into or sell or otherwise transfer its assets as an
         entirety or substantially as an entirety to, any person, or permit any
         person to consolidate with or merge into the Company, unless
         immediately after such consolidation, merger, sale or transfer, the
         Successor shall have assumed in writing the Company's obligations under
         this Agreement; and

                  (ii) not fewer than ten (10) days before the consummation of
         any consolidation of the Company with, merger by the Company into, or
         sale or other transfer by the Company of its assets as an entirety or
         substantially as an entirety to, any person, the Company shall give the
         Employee notice of that proposed transaction.

         SECTION 9.       NOTICE. Notices required or permitted to be given
by either party pursuant to this Agreement shall be in writing and shall be
deemed to have been given when delivered personally to the other party or
when deposited with the United States Postal Service as certified or
registered mail with postage prepaid and addressed:

                  (i)  if to the  Employee,  at the  Employee's  address
         last shown on the  Company's records, and

                  (ii) if to the Company, at 800 Research Parkway, Oklahoma
         City, Oklahoma 73104, directed to the attention of the Company's
         President.

or, in either case, to such other address as the party to whom or which such
notice is to be given shall have specified by notice given to the other party.

          SECTION 10.     WITHHOLDING TAXES. The Company may withhold from
all payments to be paid to the Employee pursuant to this Agreement all taxes
that, by applicable federal or state law, the Company is required to so
withhold.

         SECTION 11.       CERTAIN ADDITIONAL PAYMENTS BY THE COMPANY.

         (a)     Anything in this Agreement to the contrary notwithstanding,
in the event it shall be determined that any payment or distribution by, or
benefit from, the Company or any of its Affiliates to or for the benefit of
the Employee, whether paid or payable or distributed or distributable
pursuant to the terms of this Agreement or otherwise (any such payments,
distributions or benefits being individually referred to herein as a
"Payment," and any two or more of such payments, distributions or benefits
being referred to herein as "Payments"), would be subject to the excise tax
imposed by Section 4999 of the Code (such excise tax, together with any
interest thereon, any penalties, additions to tax, or additional amounts with
respect to such excise tax, and any interest in respect of such penalties,
additions to tax or additional amounts, being collectively referred herein to
as the "Excise Tax"), then the Employee shall be entitled to receive an
additional payment or payments (individually referred to herein as a
"Gross-Up Payment" and any two or more of such additional payments being
referred to herein as "Gross-Up Payments") in an amount such that after
payment by the Employee of all taxes (as defined in Section 11(k)) imposed
upon the Gross-Up Payment, the Employee retains an amount of such Gross-Up
Payment equal to the Excise Tax imposed upon the Payments.
<PAGE>

         (b) Subject to the provisions of Section 11(c) through (i), any
determination (individually, a "Determination") required to be made under
this Section 11(b), including whether a Gross-Up Payment is required and the
amount of such Gross-Up Payment, shall initially be made, at the Company's
expense, by nationally recognized tax counsel mutually acceptable to the
Company and the Employee ("Tax Counsel"). Tax Counsel shall provide detailed
supporting legal authorities, calculations, and documentation both to the
Company and the Employee within 15 business days of the termination of the
Employee's employment, if applicable, or such other time or times as is
reasonably requested by the Company or the Employee. If Tax Counsel makes the
initial Determination that no Excise Tax is payable by the Employee with
respect to a Payment or Payments, it shall furnish the Employee with an
opinion reasonably acceptable to the Employee that no Excise Tax will be
imposed with respect to any such Payment or Payments. The Employee shall have
the right to dispute any Determination (a "Dispute") within 15 business days
after delivery of Tax Counsel's opinion with respect to such Determination.
The Gross-Up Payment, if any, as determined pursuant to such Determination
shall, at the Company's expense, be paid by the Company to the Employee
within five business days of the Employee's receipt of such Determination.
The existence of a Dispute shall not in any way affect the Employee's right
to receive the Gross-Up Payment in accordance with such Determination. If
there is no Dispute, such Determination shall be binding, final and
conclusive upon the Company and the Employee, subject in all respects,
however, to the provisions of Section 11(c) through (i) below. As a result of
the uncertainty in the application of Sections 4999 and 280G of the Code, it
is possible that Gross-Up Payments (or portions thereof) which will not have
been made by the Company should have been made ("Underpayment"), and if upon
any reasonable written request from the Employee or the Company to Tax
Counsel, or upon Tax Counsel's own initiative, Tax Counsel, at the Company's
expense, thereafter determines that the Employee is required to make a
payment of any Excise Tax or any additional Excise Tax, as the case may be,
Tax Counsel shall, at the Company's expense, determine the amount of the
Underpayment that has occurred and any such Underpayment shall be promptly
paid by the Company to the Employee.

         (c) The Company shall defend, hold harmless, and indemnify the
Employee on a fully grossed-up after tax basis from and against any and all
claims, losses, liabilities, obligations, damages, impositions, assessments,
demands, judgements, settlements, costs and expenses (including reasonable
attorneys', accountants', and experts' fees and expenses) with respect to any
tax liability of the Employee resulting from any Final Determination (as
defined in Section 11(j)) that any Payment is subject to the Excise Tax.

         (d) If a party hereto receives any written or oral communication
with respect to any question, adjustment, assessment or pending or threatened
audit, examination, investigation or administrative, court or other
proceeding which, if pursued successfully, could result in or give rise to a
claim by the Employee against the Company under this Section 11 ("Claim"),
including, but not limited to, a claim for indemnification of the Employee by
the Company under Section 11(c), then such party shall promptly notify the
other party hereto in writing of such Claim ("Tax Claim Notice").

         (e) If a Claim is asserted against the Employee ("Employee Claim"),
the Employee shall take or cause to be taken such action in connection with
contesting such Employee Claim as the Company shall reasonably request in
writing from time to time, including the retention of counsel and experts as
are reasonably designated by the Company (it being understood and agreed by
the parties hereto that the terms of any such retention shall expressly
provide that the Company shall be solely responsible for the payment of any
and all fees and disbursements of such counsel and any experts) and the
execution of powers of attorney, PROVIDED that:

                  (i) within 30 calendar days after the Company receives or
         delivers, as the case may be, the Tax Claim Notice relating to such
         Employee Claim (or such earlier date that any payment of the taxes
         claimed is due from the Employee, but in no event sooner than five
         calendar days after the Company receives or delivers such Tax Claim
         Notice), the Company shall have notified the Employee in writing
         ("Election Notice") that the Company does not dispute its obligations
         (including, but not limited to, its indemnity obligations) under this
         Agreement and that the Company elects to contest, and to control the
         defense or prosecution of, such Employee Claim at the Company's sole
         risk and sole cost and expense; and

                  (ii) the Company shall have advanced to the Employee on an
         interest-free basis, the total amount of the tax claimed in order for
         the Employee, at the Company's request, to pay or cause to be paid the
         tax claimed, file a claim for refund of such tax and, subject to the
         provisions of the last sentence of Section 11(g), sue for a refund of
         such tax if such claim for refund is disallowed by the appropriate
         taxing authority (it being understood and agreed by the parties hereto
         that the Company shall only be entitled to sue for a refund and the
         Company shall not be entitled to initiate any proceeding in, for
         example, United States Tax Court) and shall indemnify
<PAGE>
         and hold the Employee harmless, on a fully grossed-up after tax basis,
         from any tax imposed with respect to such advance or with respect to
         any imputed income with respect to such advance; and

                  (iii) the Company shall reimburse the Employee for any and all
         costs and expenses resulting from any such request by the Company and
         shall indemnify and hold the Employee harmless, on fully grossed-up
         after-tax basis, from any tax imposed as a result of such
         reimbursement.

         (f) Subject to the provisions of Section 11(e) hereof, the Company
shall have the right to defend or prosecute, at the sole cost, expense and
risk of the Company, such Employee Claim by all appropriate proceedings,
which proceedings shall be defended or prosecuted diligently by the Company
to a Final Determination; PROVIDED, HOWEVER, that (i) the Company shall not,
without the Employee's prior written consent, enter into any compromise or
settlement of such Employee Claim that would adversely affect the Employee,
(ii) any request from the Company to the Employee regarding any extension of
the statute of limitations relating to assessment, payment, or collection of
taxes for the taxable year of the Employee with respect to which the
contested issues involved in, and amount of, the Employee Claim relate is
limited solely to such contested issues and amount, and (iii) the Company's
control of any contest or proceeding shall be limited to issues with respect
to the Employee Claim and the Employee shall be entitled to settle or
contest, in his sole and absolute discretion, any other issue raised by the
Internal Revenue Service or any other taxing authority. So long as the
Company is diligently defending or prosecuting such Employee Claim, the
Employee shall provide or cause to be provided to the Company any information
reasonably requested by the Company that relates to such Employee Claim, and
shall otherwise cooperate with the Company and its representatives in good
faith in order to contest effectively such Employee Claim. The Company shall
keep the Employee informed of all developments and events relating to any
such Employee Claim (including, without limitation, providing to the Employee
copies of all written materials pertaining to any such Employee Claim), and
the Employee or his authorized representatives shall be entitled, at the
Employee's expense, to participate in all conferences, meetings and
proceedings relating to any such Employee Claim.

         (g) If, after actual receipt by the Employee of an amount of a tax
claimed (pursuant to an Employee Claim) that has been advanced by the Company
pursuant to Section 11(e)(ii) hereof, the extent of the liability of the
Company hereunder with respect to such tax claimed has been established by a
Final Determination, the Employee shall promptly pay or cause to be paid to
the Company any refund actually received by, or actually credited to, the
Employee with respect to such tax (together with any interest paid or
credited thereon by the taxing authority and any recovery of legal fees from
such taxing authority related thereto), except to the extent that any amounts
are then due and payable by the Company to the Employee, whether under the
provisions of this Agreement or otherwise. If, after the receipt by the
Employee of an amount advanced by the Company pursuant to Section 11(e)(ii),
a determination is made by the Internal Revenue Service or other appropriate
taxing authority that the Employee shall not be entitled to any refund with
respect to such tax claimed and the Company does not notify the Employee in
writing of its intent to contest such denial of refund prior to the
expiration of 30 days after such determination, then such advance shall be
forgiven and shall not be required to be repaid and the amount of such
advance shall offset, to the extent thereof, the amount of any Gross-Up
Payments and other payments required to be paid hereunder.

         (h) With respect to any Employee Claim, if the Company fails to
deliver an Election Notice to the Employee within the period provided in
Section 11(e)(i) hereof or, after delivery of such Election Notice, the
Company fails to comply with the provisions of Section 11(e)(ii) and (iii)
and (f) hereof, then the Employee shall at any time thereafter have the right
(but not the obligation), at his election and in his sole and absolute
discretion, to defend or prosecute, at the sole cost, expense and risk of the
Company, such Employee Claim. The Employee shall have full control of such
defense or prosecution and such proceedings, including any settlement or
compromise thereof. If requested by the Employee, the Company shall
cooperate, and shall cause its Affiliates to cooperate, in good faith with
the Employee and his authorized representatives in order to contest
effectively such Employee Claim. The Company may attend, but not participate
in or control, any defense, prosecution, settlement or compromise of any
Employee Claim controlled by the Employee pursuant to this Section 11(h) and
shall bear its own costs and expenses with respect thereto. In the case of
any Employee Claim that is defended or prosecuted by the Employee, the
Employee shall, from time to time, be entitled to current payment, on a fully
grossed-up after tax basis, from the Company with respect to costs and
expenses incurred by the Employee in connection with such defense or
prosecution.

         (i) In the case of any Employee Claim that is defended or prosecuted
to a Final Determination pursuant to the terms of this Section 11(i), the
Company shall pay, on a fully grossed-up after tax basis, to the Employee in
immediately available funds the full amount of any taxes arising or resulting
from or incurred in connection with such Employee Claim that have not
theretofore been paid by the Company to the Employee,
<PAGE>

together with the costs and expenses, on a fully grossed-up after tax basis,
incurred in connection therewith that have not theretofore been paid by the
Company to the Employee, within ten calendar days after such Final
Determination. In the case of any Employee Claim not covered by the preceding
sentence, the Company shall pay, on a fully grossed-up after tax basis, to
the Employee in immediately available funds the full amount of any taxes
arising or resulting from or incurred in connection with such Employee Claim
at least ten calendar days before the date payment of such taxes is due from
the Employee, except where payment of such taxes is sooner required under the
provisions of this Section 11(i), in which case payment of such taxes (and
payment, on a fully grossed-up after tax basis, of any costs and expenses
required to be paid under this Section 11(i) shall be made within the time
and in the manner otherwise provided in this Section 11(i).

         (j) For purposes of this Agreement, the term "Final Determination"
shall mean (A) a decision, judgment, decree or other order by a court or
other tribunal with appropriate jurisdiction, which has become final and
non-appealable; (B) a final and binding settlement or compromise with an
administrative agency with appropriate jurisdiction, including, but not
limited to, a closing agreement under Section 7121 of the Code; (C) any
disallowance of a claim for refund or credit in respect to an overpayment of
tax unless a suit is filed on a timely basis; or (D) any final disposition by
reason of the expiration of all applicable statutes of limitations.

         (k) For purposes of this Agreement, the terms "tax" and "taxes" mean
any and all taxes of any kind whatsoever (including, but not limited to, any
and all Excise Taxes, income taxes, and employment taxes), together with any
interest thereon, any penalties, additions to tax, or additional amounts with
respect to such taxes and any interest in respect of such penalties,
additions to tax, or additional amounts.

         SECTION 12.     EXPENSES OF ENFORCEMENT. If a Change in Control of
the Company shall have occurred before the expiration of the term of this
Agreement, then, upon demand by the Employee made to the Company, the Company
shall reimburse the Employee for the reasonable expenses (including
attorneys' fees and expenses) incurred by the Employee in enforcing or
seeking to enforce the payment of any amount or other benefit to which the
Employee shall have become entitled pursuant to this Agreement, including
those incurred in connection with any arbitration initiated pursuant to
Section 20. To the extent that any such reimbursement would be subject to the
Excise Tax, then the Employee shall be entitled to receive Gross-Up Payments
in an amount such that after payment by the Employee of all taxes imposed on
such Gross-Up Payments, the Employee retains an amount equal to the Excise
Tax imposed upon the reimbursement, and the other provisions of Section 11
hereof shall also apply to such circumstance unless the context thereof
otherwise indicates.

         SECTION 13.      EMPLOYMENT BY WHOLLY OWNED ENTITIES. If, at or
after the Effective Date, the Employee is or becomes an employee of one or
more corporations, partnerships, limited liability companies or other
entities that are, directly or indirectly, wholly owned by the Company
("Wholly Owned Entities"), references in this Agreement to the Employee's
employment by the Company shall include the Employee's employment by any such
Wholly Owned Entity.

         SECTION 14.       NO OBLIGATION TO MITIGATE; NO RIGHTS OF OFFSET.

         (a) The Employee shall not be required to mitigate the amount of any
payment or other benefit required to be paid to the Employee pursuant to this
Agreement, whether by seeking other employment or otherwise, nor shall the
amount of any such payment or other benefit be reduced on account of any
compensation earned by the Employee as a result of employment by another
person.

         (b) The Company's obligation to make the payments provided for in
this Agreement and otherwise to perform its obligations hereunder shall not
be affected by any set-off, counterclaim, recoupment, defense or other claim,
right or action which the Company may have against the Employee or others.

         SECTION 15.      AMENDMENT AND WAIVER. No provision of this
Agreement may be amended or waived (whether by act or course of conduct or
omission or otherwise) unless that amendment or waiver is by written
instrument signed by the parties hereto. No waiver by either party of any
breach of this Agreement shall be deemed a waiver of any other or subsequent
breach.

          SECTION 16.     GOVERNING LAW. The validity, interpretation,
construction and enforceability of this Agreement shall be governed by the
laws of the State of Oklahoma.
<PAGE>

          SECTION 17.     VALIDITY. The invalidity or unenforceability of any
provision of this Agreement shall not affect the validity or enforceability
of any other provision of this Agreement, which shall remain in full force
and effect.

          SECTION 18.     COUNTERPARTS. This Agreement may be executed in
counterparts, each of which shall be deemed an original but all of which
together will constitute the same instrument.

          SECTION 19.     ASSIGNMENT. This Agreement shall inure to the
benefit of and be enforceable by the Employee's legal representative. The
Company may not assign any of its obligations under this Agreement unless (i)
such assignment is to a Successor and (ii) the requirements of Section 8 are
fulfilled.

         SECTION 20.      ARBITRATION. Except as otherwise explicitly
provided in Section 11, any dispute between the parties arising out of this
Agreement, whether as to this Agreement's construction, interpretation or
enforceability or as to any party's breach or alleged breach of any provision
of this Agreement, shall be submitted to arbitration in accordance with the
following procedures:

                  (i) Either party may demand such arbitration by giving notice
         of that demand to the other party. The notice shall state (x) the
         matter in controversy, and (y) the name of the arbitrator selected by
         the party giving the notice.

                  (ii) Not more than 15 days after such notice is given, the
         other party shall give notice to the party who demanded arbitration of
         the name of the arbitrator selected by the other party. If the other
         party shall fail to timely give such notice, the arbitrator that the
         other party was entitled to select shall be named by the Arbitration
         Committee of the American Arbitration Association. Not more than 15
         days after the second arbitrator is so named, the two arbitrators shall
         select a third arbitrator. If the two arbitrators shall fail to timely
         select a third arbitrator, the third arbitrator shall be named by the
         Arbitration Committee of the American Arbitration Association.

                  (iii) The dispute shall be arbitrated at a hearing that shall
         be concluded within ten days immediately following the date the dispute
         is submitted to arbitration unless a majority of the arbitrators shall
         elect to extend the period of arbitration. Any award made by a majority
         of the arbitrators (x) shall be made within ten days following the
         conclusion of the arbitration hearing, (y) shall be conclusive and
         binding on the parties, and (z) may be made the subject of a judgment
         of any court having jurisdiction.

                  (iv) All expenses of the arbitration shall be borne by the
         Company.

The agreement of the parties contained in the foregoing provisions of this
Section 20 shall be a complete defense to any action, suit or other
proceeding instituted in any court or before any administrative tribunal with
respect to any dispute between the parties arising out of this Agreement.

         SECTION 21.       INTERPRETATION.

(a) As used in this Agreement, the following terms and phrases have the
indicated meanings:

                  (i) "Affiliate" and "Affiliates" mean, when used with respect
         to any entity, individual, or other person, any other entity,
         individual, or other person which, directly or indirectly, through one
         or more intermediaries controls, or is controlled by, or is under
         common control with such entity, individual or person.

                  (ii) "Base Salary" has the meaning assigned to that term in
         Section 5.

                  (iii) "Basic Benefit Plans" has the meaning assigned to that
         term in Section 5.

                  (iv) "Benchmark Bonus" has the meaning assigned to that term
         in Section 5.

                  (v) "Board of Directors" means the Board of Directors of the
         Company.
<PAGE>

                  (vi) "Change in Control of the Company" has the meaning
         assigned to that phrase in Section 2.

                  (vii) "Claim" has the meaning assigned to such term in Section
         11.

                  (viii) "Code" means the Internal Revenue Code of 1986, as
         amended from time to time.

                  (ix) "Commission" means the United States Securities and
         Exchange Commission or any successor agency.

                  (x) "Company" has the meaning assigned to that term in the
         preamble to this Agreement. The term "Company" shall also include any
         Successor, whether the liability of such Successor under this Agreement
         is established by contract or occurs by operation of law.

                 (xi) "Determination" has the meaning assigned to that term in
         Section 11.

                (xii) "Dispute" has the meaning assigned to that term in
         Section 11.

               (xiii) "Effective Date" has the meaning assigned to that term
         in the preamble to this Agreement.

                (xiv) "Election Notice" has the meaning assigned to such term
         in Section 11.

                 (xv) "Employee" has the meaning assigned to such term in the
         preamble to this Agreement.

                (xvi) "Employee Claim" has the meaning assigned to such term
         in Section 11.

               (xvii) "Employee's Disability" means:

                           (A) if no Change in Control of the Company shall have
                  occurred before the date of determination, the physical or
                  mental disability of the Employee determined in accordance
                  with the disability policy of the Company at the time in
                  effect and generally applicable to its salaried employees; and

                           (B) if a Change in Control of the Company shall have
                  occurred at that date, the physical or mental disability of
                  the Employee determined in accordance with the disability
                  policy of the Company in effect immediately before the
                  occurrence of the first Change in Control of the Company and
                  generally applicable to its salaried employees.

         The Employee's Disability, and the automatic termination of the
         Employee's employment by the Company by reason of the Employee's
         Disability, shall be deemed to have occurred on the date of
         determination, PROVIDED that if (1) a Change in Control of the Company
         shall have occurred before the expiration of the term of this
         Agreement, (2) the Company shall have subsequently given notice
         pursuant to Section 6 of the Company's determination of the Employee's
         Disability, and (3) the Employee shall have given notice to the Company
         that the Employee disagrees with that determination, then (A) whether
         the Employee's Disability shall have occurred shall be submitted to
         arbitration pursuant to Section 20, and (B) if a majority of the
         arbitrators decide that the Employee's Disability had not occurred, at
         the date of determination by the Company, then (I) the Employee's
         Disability, and the automatic termination of the Employee's employment
         by the Company by reason of the Employee's Disability, shall be deemed
         not to have occurred, and (II) on demand by the Employee made to the
         Company, the Company shall reimburse the Employee for the reasonable
         expenses (including attorneys' fees and expenses) incurred by the
         Employee in obtaining that decision.
<PAGE>

                  (xviii) "Employee's Retirement" means (x) if no Change in
         Control of the Company shall have occurred before the date of the
         Employee's proposed retirement, the retirement of the Employee in
         accordance with the retirement policy of the Company at the time in
         effect and generally applicable to its salaried employees, and (y) if a
         Change in Control of the Company shall have occurred at that date, the
         retirement of the Employee from the employ of the Company in accordance
         with the retirement policy of the Company in effect immediately before
         the occurrence of the first Change in Control of the Company and
         generally applicable to its salaried employees.

                  (xix) "Event of Termination for Good Reason" has the meaning
         assigned to that phrase in Section 5.

                   (xx) "Event of Termination for Cause" has the meaning
         assigned to that phrase in Section 4.

                  (xxi) "Exchange Act" means the Securities Exchange Act of
         1934, as amended from time to time.

                 (xxii) "Excise Tax" has the meaning assigned to that term in
         Section 11.

                (xxiii) "Expiration Date" has the meaning assigned to that
         term in Section 3.

                 (xxiv) "Final Determination" has the meaning assigned to such
         term in Section 11.

                  (xxv) "Gross-Up Payment" has the meaning assigned to that term
         in Section 11.

                 (xxvi) "Other Benefit Plans" has the meaning assigned to that
         term in Section 5.

                (xxvii) "Payment" has the meaning assigned to that term in
         Section 11.

               (xxviii) "person" means any individual, corporation,
         partnership, joint venture, association, joint-stock company, limited
         partnership, limited liability company, trust, unincorporated
         organization, government, or agency or political subdivision of any
         government.

                 (xxix) "Relevant Period" means a period beginning on the
         Termination Date and ending on the first to occur of (x) the last day
         of the 18th calendar month immediately following the calendar month in
         which the Termination Date occurs, (y) the date on which the Employee
         becomes a full time employee of another person and (z) the Employee's
         normal retirement date, determined in accordance with the retirement
         policy of the Company in effect on the Termination Date.

                  (xxx) "Severance Payment" has the meaning assigned to that
         term in Section 7.

                 (xxxi) "Successor" means a person with or into which the
         Company shall have been merged or consolidated or to which the Company
         shall have transferred its assets as an entirety or substantially as an
         entirety.

                (xxxii) "Tax" has the meaning assigned to that term in Section
         11.

               (xxxiii) "Tax Claim Notice" has the meaning assigned to that
         term in Section 11.

                (xxxiv) "Tax Counsel" has the meaning assigned to that term in
         Section 11.

                 (xxxv) "Termination Date" has the meaning assigned to that
         term in Section 6.

                (xxxvi) "this Agreement" means this Change in Control
         Agreement as it may be amended from time to time in accordance with
         Section 15.

               (xxxvii) "Underpayment" has the meaning assigned to that term
         in Section 11.
<PAGE>

              (xxxviii) "Voting Stock" means shares of capital stock of the
         Company the holders of which are entitled to vote for the election of
         directors, but excluding shares entitled to so vote only upon the
         occurrence of a contingency unless that contingency shall have
         occurred.

                (xxxix) "Wholly Owned Entities" has the meaning assigned to
         that term in Section 13.

         (b) In the event of the enactment of any successor provision to any
statute or rule cited in this Agreement, references in this Agreement to such
statute or rule shall be to such successor provision.

         (c) The headings of Sections of this Agreement shall not control the
meaning or interpretation of this Agreement.

         (d) References in this Agreement to any Section are to the
corresponding Section of this Agreement unless the context otherwise indicates.

         IN WITNESS WHEREOF, the Company and the Employee have executed this
Agreement as of the Effective Date.

                                    "COMPANY"

                                  UROCOR, INC.

                                  By_____________________________________
                                  Name:__________________________________
                                  Title:_________________________________

                                   "EMPLOYEE"

                                    -------------------------------------
                                    Name:________________________________
<PAGE>

                                  SCHEDULE 10.1

                          CHANGE IN CONTROL AGREEMENTS

<TABLE>
<CAPTION>

NAME                                                                                                PERCENT
-----                                                                                               -------
<S>                                                                                                 <C>

Michael W. George, Chief Executive Officer and President                                             50%

Bruce C. Hayden, Senior Vice President and Chief Financial Officer                                   30%

Karl K. Nigg, Senior Vice President and General Manager, Sales, Marketing and Operations             40%

John L. Armstrong, Jr., Vice President for Business Development                                      35%

Robert W. Veltri, Vice President and General Manager, UroSciences Group                              30%

Lou R. Carmichael, Vice President, Chief Compliance Officer                                          0%

Gerard J. O'Dowd, Medical Director                                                                   20%
</TABLE><PAGE>

                            STOCK PURCHASE AGREEMENT

Aurora Biosciences Corporation
11010 Torreyana Road
San Diego, California 92121

The undersigned (the "Investor"), hereby confirms its agreement with you as
follows:

1. This Stock Purchase Agreement (the "Agreement") is made as of the date set
forth below between Aurora Biosciences Corporation, a Delaware corporation (the
"Company"), and the Investor.

2. The Company has authorized the sale and issuance of up to
_______________________ shares (the "Shares") of common stock of the Company,
$.001 par value per share (the "Common Stock"), subject to adjustment by the
Company's Board of Directors, to certain investors in a private placement (the
"Offering").

3. The Company and the Investor agree that the Investor will purchase from
the Company and the Company will issue and sell to the Investor ____________
shares, for a purchase price of $_________________ per share, or an aggregate
purchase price of $____________________, pursuant to the Terms and Conditions
for Purchase of Shares attached hereto as Annex I and incorporated herein by
this reference as if fully set forth herein. Unless otherwise requested by
the Investor, certificates representing the Shares purchased by the Investor
will be registered in the Investor's name and address as set forth below.

4. The Investor represents that, except as set forth below, (a) it has had no
position, office or other material relationship within the past three years with
the Company or its affiliates, (b) neither it, nor any group of which it is a
member or to which it is related, beneficially owns (including the right to
acquire or vote) any securities of the Company and (c) it has no direct or
indirect affiliation or association with any NASD member. Exceptions:

--------------------------------------------------------------------------------
        (If no exceptions, write "none." If left blank, response will be
                             deemed to be "none.")

Please confirm that the foregoing correctly sets forth the agreement between us
by signing in the space provided below for that purpose.

                                          DATED AS OF: ___________________, 2000

                                          --------------------------------------
                                          "INVESTOR"

                                          By:
                                             -----------------------------------
                                          Print Name:
                                                     ---------------------------
                                          Title:
                                                --------------------------------
                                          Address:
                                                  ------------------------------

                                          --------------------------------------
AGREED AND ACCEPTED:
AURORA BIOSCIENCES CORPORATION

By:
   ---------------------------
Title:
      ------------------------

<PAGE>

                                     ANNEX I

                   TERMS AND CONDITIONS FOR PURCHASE OF SHARES

         1. AUTHORIZATION AND SALE OF THE SHARES. Subject to the terms and
conditions of this Agreement, the Company has authorized the sale of the Shares.

         2. AGREEMENT TO SELL AND PURCHASE THE SHARES; SUBSCRIPTION DATE.

                  2.1 At the Closing (as defined in Section 3), the Company will
sell to the Investor, and the Investor will purchase from the Company, upon the
terms and conditions hereinafter set forth, the number of Shares set forth on
the signature page to which these Terms and Conditions for Purchase of Shares
are attached as Annex I (the "Signature Page") at the purchase price set forth
on such Signature Page.

                  2.2 The Company proposes to enter into this same form of Stock
Purchase Agreement with certain other investors (the "Other Investors") and
expects to complete sales of Shares to them. (The Investor and the Other
Investors are hereinafter sometimes collectively referred to as the "Investors,"
and this Agreement and the Stock Purchase Agreements executed by the Other
Investors are hereinafter sometimes collectively referred to as the
"Agreements.") The Company will accept executed Agreements from Investors for
the purchase of Shares commencing upon the date on which the Company provides
the Investors with the proposed purchase price per Share and concluding upon the
date (the "Subscription Date") on which the Company has (i) executed Agreements
with Investors each for the purchase of Shares in the amount of at least
$10,000,000 and (ii) notified Deutsche Bank Securities, Inc. (in its capacity as
Placement Agent for the Shares, the "Placement Agent") in writing that it is no
longer accepting Agreements from Investors for the purchase of Shares.

                  2.3 Investor acknowledges that the Company intends to pay the
Placement Agent a fee in respect of the sale of Shares to the Investor.

         3. DELIVERY OF THE SHARES AT CLOSING. The completion of the purchase
and sale of the Shares (the "Closing") shall occur on Thursday, February 10,
2000 or, at the Company's discretion, on such other date within ten (10) days
thereafter at a place and time (the "Closing Date") to be specified by the
Company and the Placement Agent, and of which the Investors will be notified in
advance by the Placement Agent. At the Closing, (i) the Company shall deliver to
the Investor one or more stock certificates representing the number of Shares
set forth on the signature page hereto, each such certificate to be registered
in the name of the Investor or, if so indicated on the Stock Certificate
Questionnaire attached hereto as Exhibit A, in the name of a nominee designated
by the Investor and (ii) the Investor shall deliver immediately available funds
in the amount of the aggregate purchase price for the Shares by wire transfer to
an account designated by the Placement Agent.

         The Company's obligation to issue the Shares to the Investor shall be
subject to the following conditions, any one or more of which may be waived by
the Company: (a) receipt by the Company of the purchase price for the Shares
being purchased hereunder as set forth on the Signature Page hereto; (b)
completion of purchases and sales under the Agreements with the

                                       1
<PAGE>

Other Investors; and (c) the accuracy of the representations and warranties
made by the Investors and the fulfillment of those undertakings of the
Investors to be fulfilled prior to the Closing.

         The Investor's obligation to purchase the Shares shall be subject to
the following conditions, any one or more of which may be waived by the
Investor: (a) Investors shall have executed Agreements each for the purchase of
Shares in the amount of at least $10,000,000; and (b) the satisfaction of all of
the conditions set forth in the Engagement Letter between the Company and the
Placement Agent. Subject to clause (a) above, the Investor's obligations are
expressly not conditioned on the purchase by any or all of the other Investors
of the Shares that they have agreed to purchase from the Company.

         4. REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE COMPANY. Except as
otherwise described in the Company's regular reports on Form 10-Q and 10-K as
filed by the Company with the Securities and Exchange Commission in 1999 (the
"SEC Documents"), in the Company's press releases since September 30, 1999, and
in the other Proprietary Information disclosed by the Company to the Investor in
contemplation of this offering (including the documents incorporated by
reference therein, the "Company Information"), which qualifies the following
representations and warranties in their entirety, the Company hereby represents
and warrants to, and covenants with, the Investor, as follows:

                  4.1 ORGANIZATION. The Company is duly incorporated and
validly existing in good standing under the laws of the jurisdiction of its
organization. The Company has full power and authority to own, operate and
occupy its properties and to conduct its business as presently conducted and
is registered or qualified to do business and in good standing in each
jurisdiction in which it owns or leases property or transacts business and
where the failure to be so qualified would have a material adverse effect
upon the business, financial condition, properties or operations of the
Company ("Material Adverse Effect"), and no proceeding has been instituted in
any such jurisdiction revoking, limiting or curtailing, or seeking to revoke,
limit or curtail, such power and authority or qualification.

                  4.2 DUE AUTHORIZATION. The Company has all requisite power
and authority to execute, deliver and perform its obligations under the
Agreements, and the Agreements have been duly authorized and validly executed
and delivered by the Company and constitute legal, valid and binding
agreements of the Company enforceable against the Company in accordance with
their terms, except as rights to indemnity and contribution may be limited by
state or federal securities laws or the public policy underlying such laws,
except as enforceability may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or similar laws affecting creditors' and
contracting parties' rights generally and except as enforceability may be
subject to general principles of equity (regardless of whether such
enforceability is considered in a proceeding in equity or at law).

                  4.3 NON-CONTRAVENTION. The execution and delivery of the
Agreements, the issuance and sale of the Shares to be sold by the Company under
the Agreements, the fulfillment of the terms of the Agreements and the
consummation of the transactions contemplated thereby will not (A) conflict with
or constitute a violation of, or default (with the passage of time or otherwise)
under, (i) any material bond, debenture, note or other evidence of indebtedness,
or any material lease, contract, indenture, mortgage, deed of trust, loan
agreement, joint venture or

                                       2
<PAGE>

other agreement or instrument to which the Company is a party or by which it
or its property is bound, where such conflict, violation or default is likely
to result in a Material Adverse Effect, (ii) the charter, by-laws or other
organizational documents of the Company, or (iii) any law, administrative
regulation, ordinance or order of any court or governmental agency,
arbitration panel or authority binding upon the Company or its property,
where such conflict, violation or default is likely to result in a Material
Adverse Effect, or (B) result in the creation or imposition of any lien,
encumbrance, claim, security interest or restriction whatsoever upon any of
the material properties or assets of the Company or an acceleration of
indebtedness pursuant to any obligation, agreement or condition contained in
any material bond, debenture, note or any other evidence of indebtedness or
any material indenture, mortgage, deed of trust or any other agreement or
instrument to which the Company is a party or by which it is bound or to
which any of the property or assets of the Company is subject. No consent,
approval, authorization or other order of, or registration, qualification or
filing with, any regulatory body, administrative agency, or other
governmental body in the United States is required for the execution and
delivery of the Agreements and the valid issuance and sale of the Shares to
be sold pursuant to the Agreements, other than such as have been made or
obtained, and except for any securities filings required to be made under
federal or state securities laws.

                  4.4 CAPITALIZATION. The capitalization of the Company is
described in the Company's SEC Documents. The Company has not issued any capital
stock since September 30, 1999 other than pursuant to employee benefit plans
disclosed in the Company's SEC Documents. The Shares to be sold pursuant to the
Agreements have been duly authorized, and when issued and paid for in accordance
with the terms of the Agreements, will be duly and validly issued, fully paid
and nonassessable. The outstanding shares of capital stock of the Company have
been duly and validly issued and are fully paid and nonassessable, have been
issued in compliance with all federal and state securities laws, and were not
issued in violation of any preemptive rights or similar rights to subscribe for
or purchase securities. Except as set forth in or contemplated by the Company's
SEC Documents, there are no outstanding rights (including, without limitation,
preemptive rights), warrants or options to acquire, or instruments convertible
into or exchangeable for, any unissued shares of capital stock or other equity
interest in the Company, or any contract, commitment, agreement, understanding
or arrangement of any kind to which the Company is a party and relating to the
issuance or sale of any capital stock of the Company, any such convertible or
exchangeable securities or any such rights, warrants or options. Without
limiting the foregoing, no preemptive right, co-sale right, registration right,
right of first refusal or other similar right exists with respect to the
issuance and sale of the Shares. Except as disclosed in the Company's SEC
Documents, there are no stockholders agreements, voting agreements or other
similar agreements with respect to the Common Stock to which the Company is a
party.

                  4.5 LEGAL PROCEEDINGS. There is no material legal or
governmental proceeding pending to which the Company is a party or of which the
business or property of the Company is subject that is not disclosed in the
Company's SEC Documents.

                  4.6 NO VIOLATIONS. The Company is not in violation of its
charter, bylaws or other organizational document, or in violation of any law,
administrative regulation, ordinance or order of any court or governmental
agency, arbitration panel or authority applicable to the Company, which
violation, individually or in the aggregate, would be reasonably likely to
have a

                                       3
<PAGE>

Material Adverse Effect, or is in default (and there exists no condition
which, with the passage of time or otherwise, would constitute a default) in
the performance of any material bond, debenture, note or any other evidence
of indebtedness in any indenture, mortgage, deed of trust or any other
material agreement or instrument to which the Company is a party or by which
the Company is bound or by which the property of the Company is bound, which
would be reasonably likely to have a Material Adverse Effect.

                  4.7 GOVERNMENTAL PERMITS, ETC. With the exception of the
matters which are dealt with separately in Sections 4.1, 4.12, and 4.13, the
Company has all necessary franchises, licenses, certificates and other
authorizations from any foreign, federal, state or local government or
governmental agency, department or body that are currently necessary for the
operation of the business of the Company as currently conducted except where the
failure to currently possess could not reasonably be expected to have a Material
Adverse Effect.

                  4.8 INTELLECTUAL PROPERTY.

                     (a) The Company has ownership or license or legal right
to use all patent, copyright, trade secret, trademark, customer lists,
designs, manufacturing or other processes, computer software, systems, data
compilation, research results or other proprietary rights used in the
business of the Company and material to the Company (collectively,
"Intellectual Property") other than Intellectual Property generally available
on commercial terms from other sources. All of such patents, trademarks and
registered copyrights have been duly registered in, filed in or issued by the
United States Patent and Trademark Office, the United States Register of
Copyrights or the corresponding offices of other jurisdictions and have been
maintained and renewed in accordance with all applicable provisions of law
and administrative regulations in the United States and all such
jurisdictions.

                     (b) All material licenses or other material agreements
under which (i) the Company is granted rights in Intellectual Property, other
than Intellectual Property generally available on commercial terms from other
sources, and (ii) the Company has granted rights to others in Intellectual
Property owned or licensed by the Company, are in full force and effect and,
to the knowledge of the Company, there is no material default by the Company
thereto.

                     (c) The Company believes it has taken all steps required
in accordance with sound business practice and business judgment to establish
and preserve its ownership of all material copyright, trade secret and other
proprietary rights with respect to its products and technology.

                     (d) To the knowledge of the Company, the present
business, activities and products of the Company do not infringe any
intellectual property of any other person, except where such infringement
would not have a Material Adverse Effect on the Company. Except as described
in the Company's SEC Documents, no proceeding charging the Company with
infringement of any adversely held Intellectual Property has been filed. To
the Company's knowledge, there exists no unexpired patent or patent
application which includes claims that would be infringed by or otherwise
have a Material Adverse Effect on the Company. To the knowledge of the
Company, the Company is not making unauthorized use of any confidential
information or trade secrets of any person. Neither the Company nor, to the
knowledge of the

                                       4
<PAGE>

Company, any of its employees have any agreements or arrangements with any
persons other than the Company related to confidential information or trade
secrets of such persons or restricting any such employee's engagement in
business activities of any nature. To the Company's knowledge, the activities
of the Company or any of its employees on behalf of the Company do not
violate any such agreements or arrangements known to the Company which any
such employees have with other persons, if any.

                     (e) No proceedings have been instituted or are pending
which challenge in a material manner the rights of the Company in respect to
the Company's right to the use of the Intellectual Property. The Company has
the right to use, free and clear of material claims or rights of other
persons, all of its customer lists, designs, computer software, systems, data
compilations, and other information that are required for its products or its
business as presently conducted.

                  4.9 FINANCIAL STATEMENTS. The financial statements of the
Company and the related notes contained in the Company's SEC Documents
present fairly, in accordance with generally accepted accounting principles,
the financial position of the Company as of the dates indicated, and the
results of its operations and cash flows for the periods therein specified.
Such financial statements (including the related notes) have been prepared in
accordance with generally accepted accounting principles applied on a
consistent basis throughout the periods therein specified, except as
disclosed in the Company's SEC Documents.

                  4.10 NO MATERIAL ADVERSE CHANGE. Except as disclosed in the
Company's press releases or other Proprietary Information provided to the
Investor in contemplation of this Offering, since September 30, 1999, there
has not been (i) any Material Adverse Effect affecting the Company, (ii) any
obligation, direct or contingent, that is material to the Company considered
as one enterprise, incurred by the Company, except obligations incurred in
the ordinary course of business, (iii) any dividend or distribution of any
kind declared, paid or made on the capital stock of the Company, or (iv) any
loss or damage (whether or not insured) to the physical property of the
Company which has been sustained which has a Material Adverse Effect.

                  4.11 NASDAQ COMPLIANCE. The Company's Common Stock is
registered pursuant to Section 12(g) of the Exchange Act and is listed on The
Nasdaq National Market (the "Nasdaq Stock Market"), and the Company has taken
no action designed to, or likely to have the effect of, terminating the
registration of the Common Stock under the Exchange Act or delisting the
Common Stock from the Nasdaq Stock Market.

                  4.12 REPORTING STATUS. The Company has filed in a timely
manner all documents that the Company was required to file under the
Securities Exchange Act of 1934, as amended (the "Exchange Act"), during the
12 months preceding the date of this Agreement. The following documents
complied in all material respects with the SEC's requirements as of their
respective filing dates, and the information contained therein as of the date
thereof did not contain an untrue statement of a material fact or omit to
state a material fact required to be stated therein or necessary to make the
statements therein in light of the circumstances under where they were made
not misleading:

                                       5
<PAGE>

                     (a) The Company's Annual Report on Form 10-K for the
year ended December 31, 1998 (the "10-K");

                     (b) The Company's Quarterly Reports on Form 10-Q for
each of the quarters ended March 31, 1999, June 30, 1999 and September 30,
1999; and

                     (c) All other documents, if any, filed by the Company
with the Securities and Exchange Commission since December 31, 1998 pursuant to
the reporting requirements of the Exchange Act.

                  4.13 LISTING. The Company shall comply with all
requirements of the National Association of Securities Dealers, Inc. with
respect to the issuance of the Shares and the listing thereof on the Nasdaq
Stock Market.

                  4.14 FOREIGN CORRUPT PRACTICES. Neither the Company nor, to
the knowledge of the Company, any agent or other person acting on behalf of
the Company, have (i) directly or indirectly, used any corporate funds for
unlawful contributions, gifts, entertainment or other unlawful expenses
related to foreign or domestic political activity, (ii) made any unlawful
payment to foreign or domestic government officials or employees or to
foreign or domestic political parties or campaigns from corporate funds,
(iii) failed to disclose fully any contribution made by the Company or made
by any person acting on its behalf and of which the Company is aware in
violation of law or (iv) violated in any material respect any provision of
the Foreign Corrupt Practices Act of 1977, as amended.

                  4.15 NO MANIPULATION OF STOCK. The Company has not taken and
will not, in violation of applicable law, take, any action outside the ordinary
course of business designed to or that might reasonably be expected to cause or
result in unlawful manipulation of the price of the Common Stock to facilitate
the sale or resale of the Shares.

                  4.16 ACCOUNTANTS. Ernst & Young LLP, who the Company expects
will express their opinion with respect to the financial statements to be
incorporated by reference from the Company's Annual Report on Form 10-K for the
year ended December 31, 1999 into the Registration Statement (as defined below)
and the Prospectus which forms a part thereof, are independent accountants as
required by the Securities Act and the rules and regulations promulgated
thereunder (the "Rules and Regulations").

                  4.17 CONTRACTS. The contracts described in the SEC Documents
or incorporated by reference therein that are material to the Company are in
full force and effect on the date hereof, and neither the Company nor, to the
Company's knowledge, any other party to such contracts is in breach of or
default under any of such contracts which would have a Material Adverse Effect.

                  4.18 TAXES. The Company has filed all necessary federal, state
and foreign income and franchise tax returns and has paid or accrued all taxes
shown as due thereon, and the Company has no knowledge of a tax deficiency which
has been or might be asserted or threatened against it which would have a
Material Adverse Effect.

                                       6
<PAGE>

                  4.19 TRANSFER TAXES. On the Closing Date, all stock
transfer or other taxes (other than income taxes) which are required to be
paid in connection with the sale and transfer of the Shares to be sold to the
Investor hereunder will be, or will have been, fully paid or provided for by
the Company and all laws imposing such taxes will be or will have been fully
complied with.

                  4.20 INVESTMENT COMPANY. The Company is not an "investment
company" or an "affiliated person" of, or "promoter" or "principal
underwriter" for an investment company, within the meaning of the Investment
Company Act of 1940, as amended.

                  4.21 INSURANCE. The Company maintains and will continue to
maintain insurance of the types and in the amounts that the Company
reasonably believes is adequate for its business, including, but not limited
to, insurance covering all real and personal property owned or leased by the
Company against theft, damage, destruction, acts of vandalism and all other
risks customarily insured against by similarly situated companies, all of
which insurance is in full force and effect.

                  4.22 LEGAL OPINION. The Company shall cause to be delivered
to the Investors and the Placement Agent by counsel to the Company a
customary legal opinion pertaining to Rule 10b-5 under the Securities
Exchange Act of 1934 and to the availability of an exemption from the
registration provisions of the Securities Act.

                  4.23 OFFERING MATERIALS. Other than the SEC Documents (the
"Offering Materials"), the Company has not distributed and will not
distribute prior to the Closing Date any offering material in connection with
the offering and sale of the Shares. The Company has not in the past nor will
it hereafter take any action independent of the Placement Agent to sell,
offer for sale or solicit offers to buy any securities of the Company which
would bring the offer, issuance or sale of the Shares, as contemplated by
this Agreement, within the provisions of Section 5 of the Securities Act,
unless such offer, issuance or sale was or shall be within the exemptions of
Section 4 of the Securities Act.

                  4.24 DISCLOSURE. The information contained in the SEC
Documents as of the date of such information did not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading.

         5. REPRESENTATIONS, WARRANTIES AND COVENANTS OF THE INVESTOR.

                  5.1 The Investor represents and warrants to, and covenants
with, the Company that: (i) the Investor is an "accredited investor" as
defined in Regulation D under the Securities Act and the Investor is also
knowledgeable, sophisticated and experienced in making, and is qualified to
make decisions with respect to, investments in shares presenting an
investment decision like that involved in the purchase of the Shares,
including investments in securities issued by the Company and investments in
comparable companies, and has requested, received, reviewed and considered
all information it deemed relevant in making an informed decision to purchase
the Shares; (ii) the Investor is acquiring the number of Shares set forth on
the Signature Page hereto in the ordinary course of its business and for its
own account for investment only

                                       7
<PAGE>

and with no present intention of distributing any of such Shares or any
arrangement or understanding with any other persons regarding the
distribution of such Shares; (iii) the Investor will not, directly or
indirectly, offer, sell, pledge, transfer or otherwise dispose of (or solicit
any offers to buy, purchase or otherwise acquire or take a pledge of) any of
the Shares except in compliance with the Securities Act, applicable state
securities laws and the respective rules and regulations promulgated
thereunder; (iv) the Investor has answered all questions on the Signature
Page hereto and the Investor Questionnaire attached hereto as Exhibit B for
use in preparation of the Registration Statement and the answers thereto are
true and correct as of the date hereof and will be true and correct as of the
Closing Date; (v) the Investor will notify the Company immediately of any
change in any of such information until such time as the Investor has sold
all of its Shares or until the Company is no longer required to keep the
Registration Statement effective; and (vi) the Investor has, in connection
with its decision to purchase the number of Shares set forth on the signature
page hereto, relied only upon the Company Information provided to the
Investor by the Company in contemplation of this offering and the
representations and warranties of the Company contained herein. Investor
understands that its acquisition of the Shares has not been registered under
the Securities Act of 1933, as amended (the "Securities Act"), or registered
or qualified under any state securities law in reliance on specific
exemptions therefrom, which exemptions may depend upon, among other things,
the bona fide nature of the Investor's investment intent as expressed herein.
Investor has completed or caused to be completed and delivered to the Company
the Investor Questionnaire attached hereto Exhibit B, which questionnaire is
true and correct in all material respects.

                  5.2 The Investor acknowledges, represents and agrees that
no action has been or will be taken in any jurisdiction outside the United
States by the Company or the Placement Agent that would permit an offering of
the Shares, or possession or distribution of offering materials in connection
with the issue of the Shares, in any jurisdiction outside the United States
where action for that purpose is required. Each Investor outside the United
States will comply with all applicable laws and regulations in each foreign
jurisdiction in which it purchases, offers, sells or delivers Shares or has
in its possession or distributes any offering material, in all cases at its
own expense. The Placement Agent is not authorized to make any representation
or use any information in connection with the issue, placement, purchase and
sale of the Shares.

                  5.3 The Investor hereby covenants with the Company not to
make any sale of the Shares without complying with the provisions of this
Agreement, including Section 7.2 hereof, and without effectively causing the
prospectus delivery requirement under the Securities Act to be satisfied, and
the Investor acknowledges that the certificates evidencing the Shares will be
imprinted with a legend that prohibits their transfer except in accordance
therewith. The Investor acknowledges that there may occasionally be times
when the Company, based on the advice of its counsel, determines that it must
suspend the use of the Prospectus forming a part of the Registration
Statement until such time as an amendment to the Registration Statement has
been filed by the Company and declared effective by the SEC or until the
Company has amended or supplemented such Prospectus.

                  5.4 The Investor further represents and warrants to, and
covenants with, the Company that (i) the Investor has full right, power,
authority and capacity to enter into this Agreement and to consummate the
transactions contemplated hereby and has taken all necessary action to
authorize the execution, delivery and performance of this Agreement, and (ii)
this

                                       8
<PAGE>

Agreement constitutes a valid and binding obligation of the Investor
enforceable against the Investor in accordance with its terms, except as
enforceability may be limited by applicable bankruptcy, insolvency,
reorganization, moratorium or similar laws affecting creditors' and
contracting parties' rights generally and except as enforceability may be
subject to general principles of equity (regardless of whether such
enforceability is considered in a proceeding in equity or at law) and except
as the indemnification agreements of the Investors herein may be legally
unenforceable.

                  5.5 Investor will not, prior to the effectiveness of the
Registration Statement, sell, offer to sell, solicit offers to buy, dispose
of, loan, pledge or grant any right with respect to (collectively, a
"Disposition"), the Common Stock of the Company, nor will Investor engage in
any hedging or other transaction which is designed to or could reasonably be
expected to lead to or result in a Disposition of Common Stock of the Company
by the Investor or any other person or entity. Such prohibited hedging or
other transactions would include, without limitation, effecting any short
sale or having in effect any short position (whether or not such sale or
position is against the box and regardless of when such position was entered
into) or any purchase, sale or grant of any right (including, without
limitation, any put or call option) with respect to the Common Stock of the
Company or with respect to any security (other than a broad-based market
basket or index) that includes, relates to or derives any significant part of
its value from the Common Stock of the Company.

                  5.6 The Investor understands that nothing in this Agreement
or any other materials presented to the Investor in connection with the
purchase and sale of the Shares constitutes legal, tax or investment advice.
The Investor has consulted such legal, tax and investment advisors as it, in
its sole discretion, has deemed necessary or appropriate in connection with
its purchase of Shares.

         6. SURVIVAL OF REPRESENTATIONS, WARRANTIES AND AGREEMENTS.
Notwithstanding any investigation made by any party to this Agreement or by
the Placement Agent, all covenants, agreements, representations and
warranties made by the Company and the Investor herein shall survive the
execution of this Agreement, the delivery to the Investor of the Shares being
purchased and the payment therefor.

         7. REGISTRATION OF THE SHARES; COMPLIANCE WITH THE SECURITIES ACT.

                  7.1 REGISTRATION PROCEDURES AND EXPENSES. The Company shall:

                     (a) subject to receipt of necessary information from the
Investors, prepare and file with the SEC, as soon as practicable, but in no
event later than thirty (30) days after the Closing Date, a registration
statement on Form S-3 (the "Registration Statement") to enable the resale of
the Shares by the Investors from time to time through the automated quotation
system of the Nasdaq Stock Market or in privately-negotiated transactions;

                     (b) use its reasonable efforts, subject to receipt of
necessary information from the Investors, to cause the Registration Statement
to become effective as soon as practicable, but in no event later than ninety
(90) days after the Registration Statement is filed by the Company.
Notwithstanding the foregoing, if the Registration Statement is not declared

                                       9
<PAGE>

effective by June 15, 2000 and does not remain effective for 45 continuous
days thereafter, the Investor shall be entitled to a stock dividend in the
amount of 5% of the Shares purchased by such Investor hereunder.

                     (c) use its reasonable efforts to prepare and file with
the SEC such amendments and supplements to the Registration Statement and the
Prospectus used in connection therewith as may be necessary to keep the
Registration Statement current and effective for a period not exceeding, with
respect to each Investor's Shares purchased hereunder, the earlier of (i) the
second anniversary of the Closing Date, (ii) the date on which the Investor
may sell all Shares then held by the Investor without restriction by the
volume limitations of Rule 144(e) of the Securities Act or (iii) such time as
all Shares purchased by such Investor in this Offering have been sold
pursuant to a registration statement.

                     (d) furnish to the Placement Agent and to the Investor
with respect to the Shares registered under the Registration Statement such
number of copies of the Registration Statement, Prospectuses and Preliminary
Prospectuses in conformity with the requirements of the Securities Act and
such other documents as the Investor may reasonably request, in order to
facilitate the public sale or other disposition of all or any of the Shares
by the Investor, provided, however, that the obligation of the Company to
deliver copies of Prospectuses or Preliminary Prospectuses to the Investor
shall be subject to the receipt by the Company of reasonable assurances from
the Investor that the Investor will comply with the applicable provisions of
the Securities Act and of such other securities or blue sky laws as may be
applicable in connection with any use of such Prospectuses or Preliminary
Prospectuses;

                     (e) file documents required of the Company for normal
blue sky clearance in states specified in writing by the Investor, provided,
however, that the Company shall not be required to qualify to do business or
consent to service of process in any jurisdiction in which it is not now so
qualified or has not so consented;

                     (f) bear all expenses in connection with the procedures
in paragraph (a) through (e) of this Section 7.1 and the registration of the
Shares pursuant to the Registration Statement; and

                     (g) advise the Investors, promptly after it shall
receive notice or obtain knowledge of the issuance of any stop order by the
SEC delaying or suspending the effectiveness of the Registration Statement or
of the initiation of any proceeding for that purpose; and it will promptly
use its commercially reasonable efforts to prevent the issuance of any stop
order or to obtain its withdrawal at the earliest possible moment if such
stop order should be issued.

                     (h) With a view to making available to the Investor the
benefits of Rule 144 (or its successor rule) and any other rule or regulation
of the SEC that may at any time permit the Investor to sell Shares to the
public without registration, the Company covenants and agrees to: (i) make
and keep public information available, as those terms are understood and
defined in Rule 144, until the earlier of (A) such date as all of the
Investor's Shares may be resold pursuant to Rule 144(k) or any other rule of
similar effect or (B) such date as all of the Investor's Shares shall have
been resold; (ii) file with the SEC in a timely manner all reports and other
documents required of the Company under the Securities Act and under the
Exchange Act;

                                       10
<PAGE>

and (iii) furnish to the Investor upon request, as long as the Investor owns
any Shares, (A) a written statement by the Company that it has complied with
the reporting requirements of the Securities Act and the Exchange Act, (B) a
copy of the Company's most recent Annual Report on Form 10-K or Quarterly
Report on Form 10-Q, and (C) such other information as may be reasonably
requested in order to avail the Investor of any rule or regulation of the SEC
that permits the selling of any such Shares without registration.

         It shall be a condition precedent to the obligations of the Company
to take any action pursuant to this Section 7.1 that the Investor shall
furnish to the Company such information regarding itself, the Shares to be
sold by Investor, and the intended method of disposition of such securities
as shall be required to effect the registration of the Shares.

         The Company understands that the Investor disclaims being an
underwriter, but the Investor being deemed an underwriter by the SEC shall
not relieve the Company of any obligations it has hereunder, provided,
however, that if the Company receives notification from the SEC that the
Investor is deemed an underwriter, then the period by which the Company is
obligated to submit an acceleration request to the SEC shall be extended to
the earlier of (i) the 90th day after such SEC notification, or (ii) 120 days
after the initial filing of the Registration Statement with the SEC.

                  7.2 TRANSFER OF SHARES AFTER REGISTRATION; SUSPENSION.

                     (a) The Investor agrees that it will not effect any
Disposition of the Shares or its right to purchase the Shares that would
constitute a sale within the meaning of the Securities Act except as
contemplated in the Registration Statement referred to in Section 7.1 and as
described below, and that it will promptly notify the Company of any changes
in the information set forth in the Registration Statement regarding the
Investor or its plan of distribution.

                     (b) Except in the event that paragraph (c) below
applies, the Company shall: (i) if deemed necessary by the Company, prepare
and file from time to time with the SEC a post-effective amendment to the
Registration Statement or a supplement to the related Prospectus or a
supplement or amendment to any document incorporated therein by reference or
file any other required document so that such Registration Statement will not
contain an untrue statement of a material fact or omit to state a material
fact required to be stated therein or necessary to make the statements
therein not misleading, and so that, as thereafter delivered to purchasers of
the Shares being sold thereunder, such Prospectus will not contain an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which they were made, not misleading; (ii) provide the
Investor copies of any documents filed pursuant to Section 7.2(b)(i); and
(iii) inform each Investor that the Company has complied with its obligations
in Section 7.2(b)(i) (or that, if the Company has filed a post-effective
amendment to the Registration Statement which has not yet been declared
effective, the Company will notify the Investor to that effect, will use its
reasonable efforts to secure the effectiveness of such post-effective
amendment as promptly as possible and will promptly notify the Investor
pursuant to Section 7.2(b)(i) hereof when the amendment has become effective).

                                      11
<PAGE>

                     (c) Subject to paragraph (d) below, in the event: (i) of
any request by the SEC or any other federal or state governmental authority
during the period of effectiveness of the Registration Statement for
amendments or supplements to a Registration Statement or related Prospectus
or for additional information; (ii) of the issuance by the SEC or any other
federal or state governmental authority of any stop order suspending the
effectiveness of a Registration Statement or the initiation of any
proceedings for that purpose; (iii) of the receipt by the Company of any
notification with respect to the suspension of the qualification or exemption
from qualification of any of the Shares for sale in any jurisdiction or the
initiation of any proceeding for such purpose; or (iv) of any event or
circumstance which necessitates the making of any changes in the Registration
Statement or Prospectus, or any document incorporated or deemed to be
incorporated therein by reference, so that, in the case of the Registration
Statement, it will not contain any untrue statement of a material fact or any
omission to state a material fact required to be stated therein or necessary
to make the statements therein not misleading, and that in the case of the
Prospectus, it will not contain any untrue statement of a material fact or
any omission to state a material fact required to be stated therein or
necessary to make the statements therein, in the light of the circumstances
under which they were made, not misleading; then the Company shall deliver a
certificate in writing to the Investor (the "Suspension Notice") to the
effect of the foregoing and, upon receipt of such Suspension Notice, the
Investor will refrain from selling any Shares pursuant to the Registration
Statement (a "Suspension") until the Investor's receipt of copies of a
supplemented or amended Prospectus prepared and filed by the Company, or
until it is advised in writing by the Company that the current Prospectus may
be used, and has received copies of any additional or supplemental filings
that are incorporated or deemed incorporated by reference in any such
Prospectus. In the event of any Suspension, the Company will use its
reasonable efforts to cause the use of the Prospectus so suspended to be
resumed as soon as reasonably practicable within 20 business days after
delivery of a Suspension Notice to the Investors. In addition to and without
limiting any other remedies (including, without limitation, at law or at
equity) available to the Investor, the Investor shall be entitled to specific
performance in the event that the Company fails to comply with the provisions
of this Section 7.2(c).

                     (d) Notwithstanding the foregoing paragraphs of this
Section 7.2, the Investor shall not be prohibited from selling Shares under
the Registration Statement as a result of Suspensions on more than three
occasions of not more than 30 days each in any twelve month period, unless,
in the good faith judgment of the Company's Board of Directors, upon advice
of counsel, the sale of Shares under the Registration Statement in reliance
on this paragraph 7.2(d) would be reasonably likely to cause a violation of
the Securities Act or the Exchange Act and result in potential liability to
the Company.

                     (e) Provided that a Suspension is not then in effect the
Investor may sell Shares under the Registration Statement, provided that it
arranges for delivery of a current Prospectus to the transferee of such
Shares. Upon receipt of a request therefor, the Company has agreed to provide
an adequate number of current Prospectuses to the Investor and to supply
copies to any other parties requiring such Prospectuses.

                     (f) In the event of a sale of Shares by the Investor,
the Investor must also deliver to the Company's transfer agent, with a copy
to the Company, a Certificate of

                                       12
<PAGE>

Subsequent Sale substantially in the form attached hereto as Exhibit C, so
that the shares may be properly transferred.

                  7.3 INDEMNIFICATION. For the purpose of this Section 7.3:

                     (a) the term "Selling Stockholder" shall include the
Investor and any affiliate of such Investor;

                     (b) the term "Registration Statement" shall include
any final Prospectus, exhibit, supplement or amendment included in or relating
to the Registration Statement referred to in Section 7.1; and

                     (c) the term "untrue statement" shall include any
untrue statement or alleged untrue statement, or any omission or alleged
omission to state in the Registration Statement a material fact required to be
stated therein or necessary to make the statements therein, in the light of the
circumstances under which they were made, not misleading.

                                    (i) The Company agrees to indemnify and
hold harmless each Selling Stockholder from and against any losses, claims,
damages or liabilities to which such Selling Stockholder may become subject
(under the Securities Act or otherwise) insofar as such losses, claims,
damages or liabilities (or actions or proceedings in respect thereof) arise
out of, or are based upon (i) any untrue statement of a material fact
contained in the Registration Statement, or (ii) any failure by the Company
to fulfill any undertaking included in the Registration Statement, and the
Company will reimburse such Selling Stockholder for any reasonable legal or
other expenses reasonably incurred in investigating, defending or preparing
to defend any such action, proceeding or claim, provided, however, that the
Company shall not be liable in any such case to the extent that such loss,
claim, damage or liability arises out of, or is based upon, an untrue
statement made in such Registration Statement in reliance upon and in
conformity with written information furnished to the Company by or on behalf
of such Selling Stockholder specifically for use in preparation of the
Registration Statement or the failure of such Selling Stockholder to comply
with its covenants and agreements contained in Sections 5.1, 5.2, 5.3 or 7.2
hereof or any statement or omission in any Prospectus that is corrected in
any subsequent Prospectus that was delivered to the Investor prior to the
pertinent sale or sales by the Investor.

                                    (ii) The Investor agrees to indemnify and
hold harmless the Company (and each person, if any, who controls the Company
within the meaning of Section 15 of the Securities Act, each officer of the
Company who signs the Registration Statement and each director of the
Company) from and against any losses, claims, damages or liabilities to which
the Company (or any such officer, director or controlling person) may become
subject (under the Securities Act or otherwise), insofar as such losses,
claims, damages or liabilities (or actions or proceedings in respect thereof)
arise out of, or are based upon, (i) any failure to comply with the covenants
and agreements contained in Section 5.1, 5.2, 5.3 or 7.2 hereof, or (ii) any
untrue statement of a material fact contained in the Registration Statement
if such untrue statement was made in reliance upon and in conformity with
written information furnished by or on behalf of the Investor specifically
for use in preparation of the Registration Statement, and the Investor will
reimburse the Company (or such officer, director or controlling person), as
the case

                                       13
<PAGE>

may be, for any legal or other expenses reasonably incurred in investigating,
defending or preparing to defend any such action, proceeding or claim.

                                    (iii) Promptly after receipt by any
indemnified person of a notice of a claim or the beginning of any action in
respect of which indemnity is to be sought against an indemnifying person
pursuant to this Section 7.3, such indemnified person shall notify the
indemnifying person in writing of such claim or of the commencement of such
action, but the omission to so notify the indemnifying party will not relieve
it from any liability which it may have to any indemnified party under this
Section 7.3 (except to the extent that such omission materially and adversely
affects the indemnifying party's ability to defend such action) or from any
liability otherwise than under this Section 7.3. Subject to the provisions
hereinafter stated, in case any such action shall be brought against an
indemnified person, the indemnifying person shall be entitled to participate
therein, and, to the extent that it shall elect by written notice delivered
to the indemnified party promptly after receiving the aforesaid notice from
such indemnified party, shall be entitled to assume the defense thereof, with
counsel reasonably satisfactory to such indemnified person. After notice from
the indemnifying person to such indemnified person of its election to assume
the defense thereof, such indemnifying person shall not be liable to such
indemnified person for any legal expenses subsequently incurred by such
indemnified person in connection with the defense thereof, provided, however,
that if there exists or shall exist a conflict of interest that would make it
inappropriate, in the reasonable opinion of counsel to the indemnified
person, for the same counsel to represent both the indemnified person and
such indemnifying person or any affiliate or associate thereof, the
indemnified person shall be entitled to retain its own counsel at the expense
of such indemnifying person; provided, however, that no indemnifying person
shall be responsible for the fees and expenses of more than one separate
counsel (together with appropriate local counsel) for all indemnified
parties. In no event shall any indemnifying person be liable in respect of
any amounts paid in settlement of any action unless the indemnifying person
shall have approved the terms of such settlement; provided that such consent
shall not be unreasonably withheld. No indemnifying person shall, without the
prior written consent of the indemnified person, effect any settlement of any
pending or threatened proceeding in respect of which any indemnified person
is or could have been a party and indemnification could have been sought
hereunder by such indemnified person, unless such settlement includes an
unconditional release of such indemnified person from all liability on claims
that are the subject matter of such proceeding.

                                    (iv) If the indemnification provided for
in this Section 7.3 is unavailable to or insufficient to hold harmless an
indemnified party under subsection (a) or (b) above in respect of any losses,
claims, damages or liabilities (or actions or proceedings in respect thereof)
referred to therein, then each indemnifying party shall contribute to the
amount paid or payable by such indemnified party as a result of such losses,
claims, damages or liabilities (or actions in respect thereof) in such
proportion as is appropriate to reflect the relative fault of the Company on
the one hand and the Investors on the other in connection with the statements
or omissions or other matters which resulted in such losses, claims, damages
or liabilities (or actions in respect thereof), as well as any other relevant
equitable considerations. The relative fault shall be determined by reference
to, among other things, in the case of an untrue statement, whether the
untrue statement relates to information supplied by the Company on the one
hand or an Investor on the other and the parties' relative intent, knowledge,
access to information and opportunity to correct or prevent such untrue
statement. The Company and the Investors agree

                                       14
<PAGE>

that it would not be just and equitable if contribution pursuant to this
subsection (d) were determined by pro rata allocation (even if the Investors
were treated as one entity for such purpose) or by any other method of
allocation which does not take into account the equitable considerations
referred to above in this subsection (d). The amount paid or payable by an
indemnified party as a result of the losses, claims, damages or liabilities
(or actions in respect thereof) referred to above in this subsection (d)
shall be deemed to include any legal or other expenses reasonably incurred by
such indemnified party in connection with investigating or defending any such
action or claim. Notwithstanding the provisions of this subsection (d), no
Investor shall be required to contribute any amount in excess of the amount
by which the gross amount received by the Investor from the sale of the
Shares to which such loss relates exceeds the amount of any damages which
such Investor has otherwise been required to pay by reason of such untrue
statement. No person guilty of fraudulent misrepresentation (within the
meaning of Section 11(f) of the Securities Act) shall be entitled to
contribution from any person who was not guilty of such fraudulent
misrepresentation. The Investors' obligations in this subsection to
contribute are several in proportion to their sales of Shares to which such
loss relates and not joint.

                                    (v) The parties to this Agreement hereby
acknowledge that they are sophisticated business persons who were represented
by counsel during the negotiations regarding the provisions hereof including,
without limitation, the provisions of this Section 7.3, and are fully
informed regarding said provisions. They further acknowledge that the
provisions of this Section 7.3 fairly allocate the risks in light of the
ability of the parties to investigate the Company and its business in order
to assure that adequate disclosure is made in the Registration Statement as
required by the Act and the Exchange Act. The parties are advised that
federal or state public policy as interpreted by the courts in certain
jurisdictions may be contrary to certain of the provisions of this Section
7.3, and the parties hereto hereby expressly waive and relinquish any right
or ability to assert such public policy as a defense to a claim under this
Section 7.3 and further agree not to attempt to assert any such defense.

                  7.4 TERMINATION OF CONDITIONS AND OBLIGATIONS. The
conditions precedent imposed by Section 5 or this Section 7 upon the
transferability of the Shares shall cease and terminate as to any particular
number of the Shares when such Shares shall have been effectively registered
under the Securities Act and sold or otherwise disposed of in accordance with
the intended method of disposition set forth in the Registration Statement
covering such Shares or at such time as an opinion of counsel satisfactory to
the Company shall have been rendered to the effect that such conditions are
not necessary in order to comply with the Securities Act.

                  7.5 INFORMATION AVAILABLE. So long as the Registration
Statement is effective covering the resale of Shares owned by the Investor, the
Company will furnish to the Investor:

                     (a) as soon as practicable after it is available, one
copy of (i) its Annual Report to Stockholders (which Annual Report shall
contain financial statements audited in accordance with generally accepted
accounting principles by a national firm of certified public accountants) and
(ii) if not included in substance in the Annual Report to Stockholders, its
Annual Report on Form 10-K (the foregoing, in each case, excluding exhibits);

                                       15

<PAGE>

                     (b) upon the reasonable request of the Investor, all
exhibits excluded by the parenthetical to subparagraph (a)(ii) of this
Section 7.5 as filed with the SEC and all other information that is made
available to shareholders; and

                     (c) upon the reasonable request of the Investor, an
adequate number of copies of the Prospectuses to supply to any other party
requiring such Prospectuses; and the Company, upon the reasonable request of
the Investor, will meet with the Investor or a representative thereof at the
Company's headquarters to discuss all information relevant for disclosure in
the Registration Statement covering the Shares and will otherwise cooperate
with any Investor conducting an investigation for the purpose of reducing or
eliminating such Investor's exposure to liability under the Securities Act,
including the reasonable production of information at the Company's
headquarters; provided, that the Company shall not be required to disclose
any confidential information to or meet at its headquarters with any Investor
until and unless the Investor shall have entered into a confidentiality
agreement in form and substance reasonably satisfactory to the Company with
the Company with respect thereto.

                  7.6 The Company will not issue any public statement, press
release or any other public disclosure listing Investor as one of the
purchasers of the Shares without Investor's prior written consent.

         8. NOTICES. All notices, requests, consents and other communications
hereunder shall be in writing, shall be mailed (A) if within domestic United
States by first-class registered or certified airmail, or nationally
recognized overnight express courier, postage prepaid, or by facsimile, or
(B) if delivered from outside the United States, by International Federal
Express or facsimile, and shall be deemed given (i) if delivered by
first-class registered or certified mail domestic, three business days after
so mailed, (ii) if delivered by nationally recognized overnight carrier, one
(1) business day after so mailed, (iii) if delivered by International Federal
Express, two (2) business days after so mailed, (iv) if delivered by
facsimile, upon electric confirmation of receipt and shall be delivered as
addressed as follows:

                           (a) if to the Company, to:

                               Aurora Biosciences Corporation
                               11010 Torreyana Road
                               San Diego, California 92121

                               Attn:  Stuart J.M. Collinson
                               Chief Executive Officer
                               Phone:  (858) 404-6601
                               Telecopy:  (858) 404-6716

                                       16
<PAGE>

                           (b) with a copy mailed to:

                               Cooley Godward LLP
                               4365 Executive Drive
                               San Diego, CA  92121

                               Attn: Thomas A. Coll
                               Phone: (858) 550-6013
                               Telecopy: (858) 453-3555

                           (c) if to the Investor, at its address on the
Signature Page hereto, or at such other address or addresses as may have been
furnished to the Company in writing.

         9. CHANGES. This Agreement may not be modified or amended except
pursuant to an instrument in writing signed by the Company and the Investor.

         10. HEADINGS. The headings of the various sections of this Agreement
have been inserted for convenience of reference only and shall not be deemed to
be part of this Agreement.

         11. Severability. In case any provision contained in this Agreement
should be invalid, illegal or unenforceable in any respect, the validity,
legality and enforceability of the remaining provisions contained herein shall
not in any way be affected or impaired thereby.

         12. Governing Law. This Agreement shall be governed by, and construed
in accordance with, the internal laws of the State of California, without giving
effect to the principles of conflicts of law.

         13. Counterparts. This Agreement may be executed in two or more
counterparts, each of which shall constitute an original, but all of which, when
taken together, shall constitute but one instrument, and shall become effective
when one or more counterparts have been signed by each party hereto and
delivered to the other parties.

         14. CONFIDENTIAL DISCLOSURE AGREEMENT. Notwithstanding any provision of
this Agreement to the contrary, any confidential disclosure agreement previously
executed by the Company and the Investor in connection with the transactions
contemplated by this Agreement shall remain in full force and effect in
accordance with its terms following the execution of this Agreement and the
consummation of the transactions contemplated hereby.

                                       17
<PAGE>

<TABLE>
<CAPTION>
                                    EXHIBIT A

                         AURORA BIOSCIENCES CORPORATION

                         STOCK CERTIFICATE QUESTIONNAIRE

         Pursuant to Section 5 of the Agreement, please provide us with the
following information:
<S>       <C>                                       <C>
1.        The exact name that your Shares            __________________________
          are to be registered in (this is the
          name that will appear on your stock
          certificate(s)). You may use a
          nominee name if appropriate:

2.        The relationship between the Investor      __________________________
          and the registered holder listed
          in response to item 1 above:

3.        The mailing address of the registered      __________________________
          holder listed in response to
          item 1 above:

4.        The Social Security Number or Tax          __________________________
          Identification Number of the
          registered holder listed in the
          response to item 1 above:
</TABLE>

                                       A-1
<PAGE>

                                    EXHIBIT B

                         AURORA BIOSCIENCES CORPORATION

                             INVESTOR QUESTIONNAIRE

                (ALL INFORMATION WILL BE TREATED CONFIDENTIALLY)

To:  Aurora Biosciences Corporation

         This Investor Questionnaire ("Questionnaire") must be completed by
each potential investor in connection with the offer and sale of the shares
of the common stock, par value $0.001 per share, of Aurora Biosciences
Corporation (the "Securities"). The Securities are being offered and sold by
Aurora Biosciences Corporation (the "Corporation") without registration under
the Securities Act of 1933, as amended (the "Act"), and the securities laws
of certain states, in reliance on the exemptions contained in Section 4(2) of
the Act and on Regulation D promulgated thereunder and in reliance on similar
exemptions under applicable state laws. The Corporation must determine that a
potential investor meets certain suitability requirements before offering or
selling Securities to such investor. The purpose of this Questionnaire is to
assure the Corporation that each investor will meet the applicable
suitability requirements. The information supplied by you will be used in
determining whether you meet such criteria, and reliance upon the private
offering exemption from registration is based in part on the information
herein supplied.

         This Questionnaire does not constitute an offer to sell or a
solicitation of an offer to buy any security. Your answers will be kept
strictly confidential. However, by signing this Questionnaire you will be
authorizing the Corporation to provide a completed copy of this Questionnaire
to such parties as the Corporation deems appropriate in order to ensure that
the offer and sale of the Securities will not result in a violation of the
Act or the securities laws of any state and that you otherwise satisfy the
suitability standards applicable to purchasers of the Securities. All
potential investors must answer all applicable questions and complete, date
and sign this Questionnaire. Please print or type your responses and attach
additional sheets of paper if necessary to complete your answers to any item.

A.       BACKGROUND INFORMATION

Name:__________________________________________________________________________

Business Address:______________________________________________________________
                               (Number and Street)
_______________________________________________________________________________
(City)                         (State)                    (Zip Code)

Telephone Number:(   )_________________________________________________________

Residence Address:_____________________________________________________________
                               (Number and Street)

_______________________________________________________________________________
(City)                         (State)                    (Zip Code)

Telephone Number:  (   )_______________________________________________________

If an individual:

Age:______    Citizenship:______    Where registered to vote:__________________

If a corporation, partnership, limited liability company, trust or other entity:

Type of entity:________________________________________________________________

State of formation:______________  Date of formation:_________________________

Social Security or Taxpayer Identification No.________________________________

Send all correspondence to (check one):___Residence Address __Business Address

                                       B-1
<PAGE>

B.       STATUS AS ACCREDITED INVESTOR

The undersigned is an "accredited investor" as such term is defined in
Regulation D under the Act, as at the time of the sale of the Securities the
undersigned falls within one or more of the following categories (Please
initial one or more, as applicable):(1)

_____(1) a bank as defined in Section 3(a)(2) of the Act, or a savings and
loan association or other institution as defined in Section 3(a)(5)(A) of the
Act whether acting in its individual or fiduciary capacity; a broker or
dealer registered pursuant to Section 15 of the Securities Exchange Act of
1934; an insurance company as defined in Section 2(13) of the Act; an
investment company registered under the Investment Corporation Act of 1940 or
a business development company as defined in Section 2(a)(48) of that Act; a
Small Business Investment Corporation licensed by the U.S. Small Business
Administration under Section 301(c) or (d) of the Small Business Investment
Act of 1958; a plan established and maintained by a state, its political
subdivisions, or any agency or instrumentality of a state or its political
subdivisions for the benefit of its employees, if such plan has total assets
in excess of $5,000,000; an employee benefit plan within the meaning of the
Employee Retirement Income Security Act of 1974 if the investment decision is
made by a plan fiduciary, as defined in Section 3(21) of such Act, which is
either a bank, savings and loan association, insurance company, or registered
investment adviser, or if the employee benefit plan has total assets in
excess of $5,000,000 or, if a self-directed plan, with the investment
decisions made solely by persons that are accredited investors;1

_____(2) a private business development company as defined in Section
202(a)(22) of the Investment Adviser Act of 1940;

_____(3) an organization described in Section 501(c)(3) of the Internal
Revenue Code of 1986, as amended, corporation, Massachusetts or similar
business trust, or partnership, not formed for the specific purpose of
acquiring the Securities offered, with total assets in excess of $5,000,000;

_____(4) a natural person whose individual net worth, or joint net worth with
that person's spouse, at the time of such person's purchase of the Securities
exceeds $1,000,000;

_____(5) a natural person who had an individual income in excess of $200,000
in each of the two most recent years or joint income with that person's
spouse in excess of $300,000 in each of those years and has a reasonable
expectation of reaching the same income level in the current year;

_____(6) a trust, with total assets in excess of $5,000,000, not formed for
the specific purpose of acquiring the Securities offered, whose purchase is
directed by a sophisticated person as described in Rule 506(b)(2)(ii) of
Regulation D; and

_____(7) an entity in which all of the equity owners are accredited investors
(as defined above).

-------------------------------------------------------------------------------
1 As used in this Questionnaire, the term "net worth" means the excess of total
assets over total liabilities. In computing net worth for the purpose of
subsection (4), the principal residence of the investor must be valued at cost,
including cost of improvements, or at recently appraised value by an
institutional lender making a secured loan, net of encumbrances. In determining
income, the investor should add to the investor's adjusted gross income any
amounts attributable to tax exempt income received, losses claimed as a limited
partner in any limited partnership, deductions claimed for depiction,
contributions to an IRA or KEOGH retirement plan, alimony payments, and any
amount by which income from long-term capital gains has been reduced in arriving
at adjusted gross income.

                                       B-2
<PAGE>

C.       REPRESENTATIONS

The undersigned hereby represents and warrants to the Corporation as follows:

         1. Any purchase of the Securities would be solely for the account of
the undersigned and not for the account of any other person or with a view to
any resale, fractionalization, division, or distribution thereof.

         2. The information contained herein is complete and accurate and may
be relied upon by the Corporation, and the undersigned will notify the
Corporation immediately of any material change in any of such information
occurring prior to the closing, if any, with respect to the purchase of
Securities by the undersigned or any co-purchaser.

         3. There are no suits, pending litigation, or claims against the
undersigned that could materially affect the net worth of the undersigned as
reported in this Questionnaire.

         4. The undersigned acknowledges that there may occasionally be times
when the Corporation, based on the advice of its counsel, determines that it
must suspend the use of the Prospectus forming a part of the Registration
Statement (as such terms are defined in the Stock Purchase Agreement to which
this Questionnaire is attached) until such time as an amendment to the
Registration Statement has been filed by the Company and declared effective by
the Securities and Exchange Commission or until the Corporation has amended or
supplemented such Prospectus. The undersigned is aware that, in such event, the
Securities will not be subject to ready liquidation, and that any Securities
purchased by the undersigned would have to be held during such suspension. The
overall commitment of the undersigned to investments which are not readily
marketable is not excessive in view of the undersigned's net worth and financial
circumstances, and any purchase of the Securities will not cause such commitment
to become excessive. The undersigned is able to bear the economic risk of an
investment in the Securities.

         5. In addition to reviewing the Corporation's Confidential Offering
Memorandum, the undersigned has carefully considered the potential risks
relating to the Corporation and a purchase of the Securities, and fully
understands that the Securities are speculative investments which involve a
high degree of risk of loss of the undersigned's entire investment. Among
others, the undersigned has carefully considered each of the risks described
under the heading "Risk Factors" in the Corporation's most recent annual
report on Form 10-K.

IN WITNESS WHEREOF, the undersigned has executed this Questionnaire this _____
day of _____________, 2000, and declares under oath that it is truthful and
correct.

                                 Print Name____________________________________

                                 By:___________________________________________
                                 Signature

                                 Title:________________________________________
                                       (required for any purchaser that is a
                                       corporation, partnership, trust or other
                                       entity)

                                       B-3
<PAGE>

                                    EXHIBIT C

                         AURORA BIOSCIENCES CORPORATION

                         CERTIFICATE OF SUBSEQUENT SALE

ChaseMellon Shareholder Services

         RE:      Sale of Shares of Common Stock of Aurora Biosciences
                  Corporation (the "Company") pursuant to the Company's
                  Prospectus dated _______________, 2000 (the "Prospectus")

Dear Sir/Madam:

         The undersigned hereby certifies, in connection with the sale of shares
of Common Stock of the Company included in the table of Selling Shareholders in
the Prospectus, that the undersigned has sold the Shares pursuant to the
Prospectus and in a manner described under the caption "Plan of Distribution" in
the Prospectus and that such sale complies with all applicable securities laws,
including, without limitation, the Prospectus delivery requirements of the
Securities Act of 1933, as amended.

         Selling Shareholder (the beneficial owner):___________________________

         Record Holder (e.g., if held in name of nominee):_____________________

         Restricted Stock Certificate No.(s):__________________________________

         Number of Shares Sold:________________________________________________

         Date of Sale:_________________________________________________________

         In the event that you receive a stock certificate(s) representing more
shares of Common Stock than have been sold by the undersigned, then you should
return to the undersigned a newly issued certificate for such excess shares in
the name of the Record Holder and BEARING A RESTRICTIVE LEGEND. Further, you
should place a stop transfer on your records with regard to such certificate.

                                                   Very truly yours,

                                                   By:_________________________

                                                   Print Name:_________________

                                                   Title:______________________

Dated:_____________________________

cc:      Investor Relations
         Aurora Biosciences Corporation
         11010 Torreyana Road
         San Diego, California  92121

                                       C-1
<PAGE>
<TABLE>
<CAPTION>
                                   SCHEDULE A
                                LIST OF INVESTORS
<S>                                                                        <C>                   <C>
                                                                                                   AGGREGATE
NAME AND ADDRESS                                                           SHARES                PURCHASE PRICE
---------------------------------------------------------------------   -------------     ---------------------
JANUS INVESTMENT FUND
BY: BOUYBREESE & CO.                                                       919,050                $38,600,100

JANUS INVESTMENT FUND
BY: BOOKBEND & CO.                                                         380,950                $15,999,900

BLACKROCK FUNDS
BY: BARNETT AND CO.                                                        400,000                $16,800,000

TISCH FINANCIAL MANAGEMENT
BY: BAKER BROS. INVESTMENTS, LLC                                            50,000                $ 2,100,000

TISCH FINANCIAL MANAGEMENT
BY: FOUR PARTNERS                                                           50,000                $ 2,100,000

TOTAL                                                                    1,800,000                $75,600,000
</TABLE>

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