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                                                                 Exhibit 10.19

                              PHARSIGHT CORPORATION

                           2000 EQUITY INCENTIVE PLAN

                              Adopted April 7, 2000
                      Approved By Stockholders May __, 2000
                 Effective Date: Date of Initial Public Offering
                         Termination Date: April 7, 2010

1. PURPOSES.

      (a) Eligible Stock Award Recipients. The persons eligible to receive Stock
Awards are the Employees, Directors and Consultants of the Company and its
Affiliates.

      (b) Available Stock Awards. The purpose of the Plan is to provide a means
by which eligible recipients of Stock Awards may be given an opportunity to
benefit from increases in value of the Common Stock through the granting of the
following Stock Awards: (i) Incentive Stock Options, (ii) Nonstatutory Stock
Options, (iii) stock bonuses and (iv) rights to acquire restricted stock. The
Plan also provides for non-discretionary grants of Nonstatutory Stock Options to
Non-Employee Directors of the Company.

      (c) General Purpose. The Company, by means of the Plan, seeks to retain
the services of the group of persons eligible to receive Stock Awards, to secure
and retain the services of new members of this group and to provide incentives
for such persons to exert maximum efforts for the success of the Company and its
Affiliates.

2. DEFINITIONS.

      (a) "Affiliate" means any parent corporation or subsidiary corporation of
the Company, whether now or hereafter existing, as those terms are defined in
Sections 424(e) and (f), respectively, of the Code.

      (b) "Board" means the Board of Directors of the Company.

      (c) "Cause" means the occurrence of any one or more of the following: (i)
the Participant's conviction of any felony or any crime involving moral
turpitude or dishonesty; (ii) the Participant's participation in a fraud or act
of dishonesty against the Company which results in material harm to the business
of the Company; or (iii) the Participant's intentional, material violation of
any contract between the Company and the Participant or any statutory duty the
Participant owes to the Company that the Participant does not correct within
thirty (30) days after written notice thereof has been provided to the
Participant.

      (d) "Change in Control" means the occurrence of any one or more of the
following:

            (i) a Corporate Transaction after which persons who were not
stockholders of the Company immediately prior to such Corporate Transaction own,
directly or indirectly,

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immediately following such Corporate Transaction, fifty percent (50%) or more of
the outstanding voting power of each of (a) the continuing or surviving entity
and (b) any direct or indirect parent corporation of the continuing or surviving
entity;

            (ii) after the IPO Date, an acquisition by any person, entity or
group within the meaning of Section 13(d) or 14(d) of the Exchange Act, or any
comparable successor provisions (excluding any employee benefit plan, or related
trust, sponsored or maintained by the Company or an Affiliate) of the beneficial
ownership (within the meaning of Rule 13d-3 promulgated under the Exchange Act,
or comparable successor rule) of securities of the Company representing at least
fifty percent (50%) of the combined voting power entitled to vote in the
election of Directors; provided that such acquisition does not occur in
connection with, in contemplation of or as a result of a Corporate Transaction;
or

            (iii) after the IPO Date, during any consecutive two (2) year period
the individuals who, as of the start of such period, are members of the Board
(the "Incumbent Board"), cease for any reason to constitute at least fifty
percent (50%) of the Board, provided that such change in the Incumbent Board
does not occur in connection with, in contemplation of or as a result of a
Corporate Transaction, and further provided that if the election, or nomination
for election, by the Company's stockholders of any new Director was approved by
a vote of at least fifty percent (50%) of the Incumbent Board, such new Director
shall be considered as a member of the Incumbent Board.

      (e) "Code" means the Internal Revenue Code of 1986, as amended.

      (f) "Committee" means a committee of one or more members of the Board
appointed by the Board in accordance with subsection 3(c).

      (g) "Common Stock" means the common stock of the Company.

      (h) "Company" means Pharsight Corporation, a Delaware corporation.

      (i) "Consultant" means any person, including an advisor, (i) engaged by
the Company or an Affiliate to render consulting or advisory services and who is
compensated for such services or (ii) who is a member of the Board of Directors
of an Affiliate. However, the term "Consultant" shall not include either
Directors who are not compensated by the Company for their services as Directors
or Directors who are merely paid a director's fee by the Company for their
services as Directors.

      (j) "Continuous Service" means that the Participant's service with the
Company or an Affiliate, whether as an Employee, Director or Consultant, is not
interrupted or terminated. The Participant's Continuous Service shall not be
deemed to have terminated merely because of a change in the capacity in which
the Participant renders service to the Company or an Affiliate as an Employee,
Consultant or Director or a change in the entity for which the Participant
renders such service, provided that there is no interruption or termination of
the Participant's Continuous Service. For example, a change in status from an
Employee of the Company to a Consultant of an Affiliate or a Director will not
constitute an interruption of Continuous Service. The Board or the chief
executive officer of the Company, in that party's sole discretion, may

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determine whether Continuous Service shall be considered interrupted in the case
of any leave of absence approved by that party, including sick leave, military
leave or any other personal leave.

      (k) "Corporate Transaction" means the occurrence of any one or more of the
following:

            (i) a sale, lease or other disposition of all or substantially all
of the securities or assets of the Company;

            (ii) a merger or consolidation following which the Company is not
the surviving corporation;

            (iii) a reverse merger following which the Company is the surviving
corporation but the shares of Common Stock outstanding immediately preceding the
merger are converted by virtue of the merger into other property, whether in the
form of securities, cash or otherwise; or

            (iv) any other transaction described as a "corporate transaction" in
Treasury Regulations ss.1.425-1(a)(1)(ii).

      (l) "Covered Employee" means the chief executive officer and the four (4)
other highest compensated officers of the Company for whom total compensation is
required to be reported to stockholders under the Exchange Act, as determined
for purposes of Section 162(m) of the Code.

      (m) "Director" means a member of the Board of Directors of the Company.

      (n) "Disability" means the permanent and total disability of a person
within the meaning of Section 22(e)(3) of the Code.

      (o) "Eligible Director" means a Non-Employee Director or any other
Director who is not an Employee or Consultant at the time of grant of an
Nonstatutory Stock Option under section 7 hereof.

      (p) "Employee" means any person employed by the Company or an Affiliate.
Mere service as a Director or payment of a director's fee by the Company or an
Affiliate shall not be sufficient to constitute "employment" by the Company or
an Affiliate.

      (q) "Exchange Act" means the Securities Exchange Act of 1934, as amended.

      (r) "Fair Market Value" means, as of any date, the value of the Common
Stock determined as follows:

            (i) If the Common Stock is listed on any established stock exchange
or traded on the Nasdaq National Market or the Nasdaq SmallCap Market, the Fair
Market Value of a share of Common Stock shall be the closing sales price for
such stock (or the closing bid, if no sales were reported) as quoted on such
exchange or market (or the exchange or market with the greatest volume of
trading in the Common Stock) on the last market trading day prior to the day

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of determination, as reported in The Wall Street Journal or such other source as
the Board deems reliable.

            (ii) In the absence of such markets for the Common Stock, the Fair
Market Value shall be determined in good faith by the Board.

      (s) "Good Reason" means that one or more of the following are undertaken
by the Company without the Participant's express written consent: (i) the
assignment to the Participant of any duties or responsibilities that results in
a diminution in the Participant's position or function as in effect immediately
prior to the effective date of the Change in Control; provided, however, that a
mere change in the Participant's title or reporting relationships shall not
constitute Good Reason; (ii) a reduction by the Company in the Participant's
annual base salary, as in effect on the effective date of the Change in Control;
(iii) any failure by the Company to continue in effect any benefit plan or
program, including incentive plans or plans with respect to the receipt of
securities of the Company, in which the Participant was participating
immediately prior to the effective date of the Change in Control (hereinafter
referred to as "Benefit Plans"), or the taking of any action by the Company that
would adversely affect the Participant's participation in or reduce the
Participant's benefits under the Benefit Plans or deprive the Participant of any
fringe benefit that the Participant enjoyed immediately prior to the effective
date of the Change in Control; provided, however, that Good Reason shall not be
deemed to have occurred if the Company provides for the Participant's
participation in benefit plans and programs that, taken as a whole, are
comparable to the Benefit Plans; (iv) a relocation of the Participant's business
office to a location more than thirty (30) miles from the location at which the
Participant performs duties as of the effective date of the Change in Control,
except for required travel by the Participant on the Company's business to an
extent substantially consistent with the Participant's business travel
obligations prior to the Change in Control; (v) a material breach by the Company
of any provision of the Plan or the Stock Award Agreement or any other material
agreement between the Participant and the Company concerning the terms and
conditions of the Participant's employment; or (vi) any failure by the Company
to obtain the assumption of the Plan and Stock Award Agreement by any successor
or assign of the Company.

      (t) "Incentive Stock Option" means an Option intended to qualify as an
incentive stock option within the meaning of Section 422 of the Code and the
regulations promulgated thereunder.

      (u) "IPO Date" means the effective date of the Company's Form S-1
Registration Statement filed under the Securities Act in connection with the
initial public offering of the Common Stock.

      (v) "Non-Employee Director" means a Director who either (i) is not a
current Employee or Officer of the Company or its parent or a subsidiary, does
not receive compensation (directly or indirectly) from the Company or its parent
or a subsidiary for services rendered as a consultant or in any capacity other
than as a Director (except for an amount as to which disclosure would not be
required under Item 404(a) of Regulation S-K promulgated pursuant to the
Securities Act ("Regulation S-K")), does not possess an interest in any other
transaction as to which disclosure would be required under Item 404(a) of
Regulation S-K and is not engaged in a

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business relationship as to which disclosure would be required under Item 404(b)
of Regulation S-K; or (ii) is otherwise considered a "non-employee director" for
purposes of Rule 16b-3.

      (w) "Non-Employee Director Option" shall have the meaning subscribed in
section 7 hereof.

      (x) "Non-Employee Director Option Agreement" means a written agreement
between the Company and an Eligible Director, evidencing the terms and
conditions of a Non-Employee Director Option grant. Each Non-Employee Director
Option Agreement shall be subject to the terms and conditions of the Plan.

      (y) "Nonstatutory Stock Option" means an Option not intended to qualify as
an Incentive Stock Option.

      (z) "Officer" means a person who is an officer of the Company within the
meaning of Section 16 of the Exchange Act and the rules and regulations
promulgated thereunder.

      (aa) "Option" means an Incentive Stock Option or a Nonstatutory Stock
Option granted pursuant to the Plan.

      (bb) "Option Agreement" means a written agreement between the Company and
an Optionholder evidencing the terms and conditions of an individual Option
grant. Each Option Agreement shall be subject to the terms and conditions of the
Plan.

      (cc) "Optionholder" means a person to whom an Option is granted pursuant
to the Plan or, if applicable, such other person who holds an outstanding
Option.

      (dd) "Outside Director" means a Director who either (i) is not a current
employee of the Company or an "affiliated corporation" (within the meaning of
Treasury Regulations promulgated under Section 162(m) of the Code), is not a
former employee of the Company or an "affiliated corporation" receiving
compensation for prior services (other than benefits under a tax qualified
pension plan), was not an officer of the Company or an "affiliated corporation"
at any time and is not currently receiving direct or indirect remuneration from
the Company or an "affiliated corporation" for services in any capacity other
than as a Director or (ii) is otherwise considered an "outside director" for
purposes of Section 162(m) of the Code.

      (ee) "Participant" means a person to whom a Stock Award is granted
pursuant to the Plan or, if applicable, such other person who holds an
outstanding Stock Award.

      (ff) "Plan" means this Pharsight Corporation 2000 Equity Incentive Plan.

      (gg) "Predecessor Plans" means the Company's 1995 Stock Option Plan and
the 1997 Stock Option Plan

      (hh) "Rule 16b-3" means Rule 16b-3 promulgated under the Exchange Act or
any successor to Rule 16b-3, as in effect from time to time.

      (ii) "Securities Act" means the Securities Act of 1933, as amended.

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      (jj) "Stock Award" means any right granted under the Plan, including an
Option, a Non-Employee Director Option, a stock bonus and a right to acquire
restricted stock.

      (kk) "Stock Award Agreement" means a written agreement between the Company
and a holder of a Stock Award evidencing the terms and conditions of an
individual Stock Award grant. Each Stock Award Agreement shall be subject to the
terms and conditions of the Plan.

      (ll) "Ten Percent Stockholder" means a person who owns (or is deemed to
own pursuant to Section 424(d) of the Code) stock possessing more than ten
percent (10%) of the total combined voting power of all classes of stock of the
Company or of any of its Affiliates.

3. ADMINISTRATION.

      (a) Administration by Board. The Board shall administer the Plan unless
and until the Board delegates administration to a Committee, as provided in
subsection 3(c).

      (b) Powers of Board. The Board shall have the power, subject to, and
within the limitations of, the express provisions of the Plan:

            (i) To determine from time to time which of the persons eligible
under the Plan shall be granted Stock Awards; when and how each Stock Award
shall be granted; what type or combination of types of Stock Award shall be
granted; the provisions of each Stock Award granted (which need not be
identical), including the time or times when a person shall be permitted to
receive Common Stock pursuant to a Stock Award; and the number of shares of
Common Stock with respect to which a Stock Award shall be granted to each such
person.

            (ii) To construe and interpret the Plan and Stock Awards granted
under it, and to establish, amend and revoke rules and regulations for its
administration. The Board, in the exercise of this power, may correct any
defect, omission or inconsistency in the Plan or in any Stock Award Agreement,
in a manner and to the extent it shall deem necessary or expedient to make the
Plan fully effective.

            (iii) To amend the Plan or a Stock Award as provided in Section 13.

            (iv) Generally, to exercise such powers and to perform such acts as
the Board deems necessary or expedient to promote the best interests of the
Company which are not in conflict with the provisions of the Plan.

      (c) Delegation to Committee.

            (i) General. The Board may delegate administration of the Plan to a
Committee or Committees of one (1) or more members of the Board, and the term
"Committee" shall apply to any person or persons to whom such authority has been
delegated. If administration is delegated to a Committee, the Committee shall
have, in connection with the administration of the Plan, the powers theretofore
possessed by the Board, including the power to delegate to a subcommittee any of
the administrative powers the Committee is authorized to exercise (and
references in this Plan to the Board shall thereafter be to the Committee or
subcommittee), subject, however, to such resolutions, not inconsistent with the
provisions of the

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Plan, as may be adopted from time to time by the Board. The Board may abolish
the Committee at any time and revest in the Board the administration of the
Plan.

            (ii) Committee Composition when Common Stock is Publicly Traded. At
such time as the Common Stock is publicly traded, in the discretion of the
Board, a Committee may consist solely of two or more Outside Directors, in
accordance with Section 162(m) of the Code, and/or solely of two or more
Non-Employee Directors, in accordance with Rule 16b-3. Within the scope of such
authority, the Board or the Committee may (1) delegate to a committee of one or
more members of the Board who are not Outside Directors the authority to grant
Stock Awards to eligible persons who are either (a) not then Covered Employees
and are not expected to be Covered Employees at the time of recognition of
income resulting from such Stock Award or (b) not persons with respect to whom
the Company wishes to comply with Section 162(m) of the Code and/or) (2)
delegate to a committee of one or more members of the Board who are not
Non-Employee Directors the authority to grant Stock Awards to eligible persons
who are not then subject to Section 16 of the Exchange Act.

      (d) Effect of Board's Decision. All determinations, interpretations and
constructions made by the Board in good faith shall not be subject to review by
any person and shall be final, binding and conclusive on all persons.

4. SHARES SUBJECT TO THE PLAN.

      (a) Share Reserve. Subject to the provisions of Section 12 relating to
adjustments upon changes in Common Stock, the Common Stock that may be issued
pursuant to Stock Awards shall not exceed in the aggregate four million
(4,000,000) shares of Common Stock (the "Reserved Shares"). As of each
January 1, beginning with January 1, 2001 and continuing through and
including January 1, 2010 (the "Anniversary Date"), the number of Reserved
Shares will be increased automatically by the least of (i) 5% of the total
number of shares of Common Stock outstanding on such Anniversary Date, (ii)
Two Million (2,000,000) shares, or (iii) such fewer number of shares as
determined by the Board prior to such Anniversary Date.

      (b) Reversion of Shares to the Share Reserve. If any Stock Award shall for
any reason expire or otherwise terminate, in whole or in part, without having
been exercised in full, the shares of Common Stock not acquired under such Stock
Award shall revert to and again become available for issuance under the Plan.

      (c) Source of Shares. The shares of Common Stock subject to the Plan may
be unissued shares or reacquired shares, bought on the market or otherwise.

5. ELIGIBILITY.

      (a) Eligibility for Specific Stock Awards. Incentive Stock Options may be
granted only to Employees. Stock Awards other than Incentive Stock Options may
be granted to Employees, Directors (whether or not an Eligible Director for
purposes of section 7 hereof) and Consultants.

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      (b) Ten Percent Stockholders. A Ten Percent Stockholder shall not be
granted an Incentive Stock Option unless the exercise price of such Option is at
least one hundred ten percent (110%) of the Fair Market Value of the Common
Stock at the date of grant and the Option is not exercisable after the
expiration of five (5) years from the date of grant.

      (c) Section 162(m) Limitation. Subject to the provisions of Section 12
relating to adjustments upon changes in the shares of Common Stock, no
Employee shall be eligible to be granted Options covering more than One
Million (1,000,000) shares of Common Stock during any calendar year.

      (d) Consultants.

            (i) A Consultant shall not be eligible for the grant of a Stock
Award if, at the time of grant, a Form S-8 Registration Statement under the
Securities Act ("Form S-8") is not available to register either the offer or the
sale of the Company's securities to such Consultant because of the nature of the
services that the Consultant is providing to the Company, or because the
Consultant is not a natural person, or as otherwise provided by the rules
governing the use of Form S-8, unless the Company determines both (i) that such
grant (A) shall be registered in another manner under the Securities Act (e.g.,
on a Form S-3 Registration Statement) or (B) does not require registration under
the Securities Act in order to comply with the requirements of the Securities
Act, if applicable, and (ii) that such grant complies with the securities laws
of all other relevant jurisdictions.

            (ii) Form S-8 generally is available to consultants and advisors
only if (i) they are natural persons; (ii) they provide bona fide services to
the issuer, its parents, its majority-owned subsidiaries or majority-owned
subsidiaries of the issuer's parent; and (iii) the services are not in
connection with the offer or sale of securities in a capital-raising
transaction, and do not directly or indirectly promote or maintain a market for
the issuer's securities.

6. OPTION PROVISIONS.

      Each Option shall be in such form and shall contain such terms and
conditions as the Board shall deem appropriate. All Options shall be separately
designated Incentive Stock Options or Nonstatutory Stock Options at the time of
grant, and, if certificates are issued, a separate certificate or certificates
will be issued for shares of Common Stock purchased on exercise of each type of
Option. The provisions of separate Options need not be identical, but each
Option shall include (through incorporation of provisions hereof by reference in
the Option or otherwise) the substance of each of the following provisions:

      (a) Term. Subject to the provisions of subsection 5(b) regarding Ten
Percent Stockholders, no Incentive Stock Option shall be exercisable after the
expiration of ten (10) years from the date it was granted.

      (b) Exercise Price of an Incentive Stock Option. Subject to the provisions
of subsection 5(b) regarding Ten Percent Stockholders, the exercise price of
each Incentive Stock Option shall be not less than one hundred percent (100%) of
the Fair Market Value of the Common Stock subject to the Option on the date the
Option is granted. Notwithstanding the foregoing, an Incentive Stock Option may
be granted with an exercise price lower than that set

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forth in the preceding sentence if such Option is granted pursuant to an
assumption or substitution for another option in a manner satisfying the
provisions of Section 424(a) of the Code.

      (c) Exercise Price of a Nonstatutory Stock Option. The exercise price of
each Nonstatutory Stock Option shall be not less than eighty-five percent (85%)
of the Fair Market Value of the Common Stock subject to the Option on the date
the Option is granted. Notwithstanding the foregoing, a Nonstatutory Stock
Option may be granted with an exercise price lower than that set forth in the
preceding sentence if such Option is granted pursuant to an assumption or
substitution for another option in a manner satisfying the provisions of Section
424(a) of the Code.

      (d) Consideration. The purchase price of Common Stock acquired pursuant to
an Option shall be paid, to the extent permitted by applicable statutes and
regulations, either (i) in cash at the time the Option is exercised or (ii) at
the discretion of the Board at the time of the grant of the Option (or
subsequently in the case of a Nonstatutory Stock Option) (1) by delivery to the
Company of other Common Stock, (2) according to a deferred payment or other
similar arrangement with the Optionholder or (3) in any other form of legal
consideration that may be acceptable to the Board. Unless otherwise specifically
provided in the Option, the purchase price of Common Stock acquired pursuant to
an Option that is paid by delivery to the Company of other Common Stock
acquired, directly or indirectly from the Company, shall be paid only by shares
of the Common Stock of the Company that have been held for more than six (6)
months (or such longer or shorter period of time required to avoid a charge to
earnings for financial accounting purposes). At any time that the Company is
incorporated in Delaware, payment of the Common Stock's "par value," as defined
in the Delaware General Corporation Law, shall not be made by deferred payment.

      (e) Transferability of an Incentive Stock Option. An Incentive Stock
Option shall not be transferable except by will or by the laws of descent and
distribution and shall be exercisable during the lifetime of the Optionholder
only by the Optionholder. Notwithstanding the foregoing, the Optionholder may,
by delivering written notice to the Company, in a form satisfactory to the
Company, designate a third party who, in the event of the death of the
Optionholder, shall thereafter be entitled to exercise the Option.

      (f) Transferability of a Nonstatutory Stock Option. A Nonstatutory Stock
Option shall be transferable to the extent provided in the Option Agreement. If
the Nonstatutory Stock Option does not provide for transferability, then the
Nonstatutory Stock Option shall not be transferable except by will or by the
laws of descent and distribution and shall be exercisable during the lifetime of
the Optionholder only by the Optionholder. Notwithstanding the foregoing, the
Optionholder may, by delivering written notice to the Company, in a form
satisfactory to the Company, designate a third party who, in the event of the
death of the Optionholder, shall thereafter be entitled to exercise the Option.

      (g) Vesting Generally. The total number of shares of Common Stock subject
to an Option may, but need not, vest and therefore become exercisable in
periodic installments that may, but need not, be equal. The Option may be
subject to such other terms and conditions on the time or times when it may be
exercised (which may be based on performance or other

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criteria) as the Board may deem appropriate. The vesting provisions of
individual Options may vary. The provisions of this subsection 6(g) are subject
to any Option provisions governing the minimum number of shares of Common Stock
as to which an Option may be exercised.

      (h) Termination of Continuous Service. In the event an Optionholder's
Continuous Service terminates (other than upon the Optionholder's death or
Disability), the Optionholder may exercise his or her Option (to the extent that
the Optionholder was entitled to exercise such Option as of the date of
termination) but only within such period of time ending on the earlier of (i)
the date three (3) months following the termination of the Optionholder's
Continuous Service (or such longer or shorter period specified in the Option
Agreement), or (ii) the expiration of the term of the Option as set forth in the
Option Agreement. If, after termination, the Optionholder does not exercise his
or her Option within the time specified in the Option Agreement, the Option
shall terminate.

      (i) Extension of Termination Date. An Optionholder's Option Agreement may
also provide that if the exercise of the Option following the termination of the
Optionholder's Continuous Service (other than upon the Optionholder's death or
Disability) would be prohibited at any time solely because the issuance of
shares of Common Stock would violate the registration requirements under the
Securities Act, then the Option shall terminate on the earlier of (i) the
expiration of the term of the Option set forth in subsection 6(a) or (ii) the
expiration of a period of three (3) months after the termination of the
Optionholder's Continuous Service during which the exercise of the Option would
not be in violation of such registration requirements.

      (j) Disability of Optionholder. In the event that an Optionholder's
Continuous Service terminates as a result of the Optionholder's Disability, the
Optionholder may exercise his or her Option (to the extent that the Optionholder
was entitled to exercise such Option as of the date of termination), but only
within such period of time ending on the earlier of (i) the date twelve (12)
months following such termination (or such longer or shorter period specified in
the Option Agreement) or (ii) the expiration of the term of the Option as set
forth in the Option Agreement. If, after termination, the Optionholder does not
exercise his or her Option within the time specified herein, the Option shall
terminate.

      (k) Death of Optionholder. In the event (i) an Optionholder's Continuous
Service terminates as a result of the Optionholder's death or (ii) the
Optionholder dies within the period (if any) specified in the Option Agreement
after the termination of the Optionholder's Continuous Service for a reason
other than death, then the Option may be exercised (to the extent the
Optionholder was entitled to exercise such Option as of the date of death) by
the Optionholder's estate, by a person who acquired the right to exercise the
Option by bequest or inheritance or by a person designated to exercise the
Option upon the Optionholder's death pursuant to subsection 6(e) or 6(f), but
only within the period ending on the earlier of (1) the date eighteen (18)
months following the date of death (or such longer or shorter period specified
in the Option Agreement) or (2) the expiration of the term of such Option as set
forth in the Option Agreement. If, after death, the Option is not exercised
within the time specified herein, the Option shall terminate.

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      (l) Early Exercise. The Option may, but need not, include a provision
whereby the Optionholder may elect at any time before the Optionholder's
Continuous Service terminates to exercise the Option as to any part or all of
the shares of Common Stock subject to the Option prior to the full vesting of
the Option. Any unvested shares of Common Stock so purchased may be subject to a
repurchase option in favor of the Company or to any other restriction the Board
determines to be appropriate.

      (m) Re-Load Options.

            (i) Without in any way limiting the authority of the Board to make
or not to make grants of Options hereunder, the Board shall have the authority
(but not an obligation) to include as part of any Option Agreement a provision
entitling the Optionholder to a further Option (a "Re-Load Option") in the event
the Optionholder exercises the Option evidenced by the Option Agreement, in
whole or in part, by surrendering other shares of Common Stock in accordance
with this Plan and the terms and conditions of the Option Agreement. Unless
otherwise specifically provided in the Option, the Optionholder shall not
surrender shares of Common Stock acquired, directly or indirectly from the
Company, unless such shares have been held for more than six (6) months (or such
longer or shorter period of time required to avoid a charge to earnings for
financial accounting purposes).

            (ii) Any such Re-Load Option shall (1) provide for a number of
shares of Common Stock equal to the number of shares of Common Stock surrendered
as part or all of the exercise price of such Option; (2) have an expiration date
which is the same as the expiration date of the Option the exercise of which
gave rise to such Re-Load Option; and (3) have an exercise price which is equal
to one hundred percent (100%) of the Fair Market Value of the Common Stock
subject to the Re-Load Option on the date of exercise of the original Option.
Notwithstanding the foregoing, a Re-Load Option shall be subject to the same
exercise price and term provisions heretofore described for Options under the
Plan.

            (iii) Any such Re-Load Option may be an Incentive Stock Option or a
Nonstatutory Stock Option, as the Board may designate at the time of the grant
of the original Option; provided, however, that the designation of any Re-Load
Option as an Incentive Stock Option shall be subject to the one hundred thousand
dollar ($100,000) annual limitation on the exercisability of Incentive Stock
Options described in subsection 11(d) and in Section 422(d) of the Code. There
shall be no Re-Load Options on a Re-Load Option. Any such Re-Load Option shall
be subject to the availability of sufficient shares of Common Stock under
subsection 4(a) and the "Section 162(m) Limitation" on the grants of Options
under subsection 5(c) and shall be subject to such other terms and conditions as
the Board may determine which are not inconsistent with the express provisions
of the Plan regarding the terms of Options.

7. NON-EMPLOYEE DIRECTOR STOCK OPTIONS

      Without any further action from the Board, each Eligible Director shall be
granted Nonstatutory Stock Options as described in subsections 7(a) and 7(b)
(collectively, the "Non-

                                       11
<PAGE>

Employee Director Options"). Each Non-Employee Director Option shall include the
substance of the terms set forth in subsection 7(c) through 7(k) and such other
terms and conditions as shall be determined by the Board as appropriate.

      (a) Initial Grants and Interim Grants.

            (i) On the IPO Date, each Eligible Director who has not received a
Stock Award under any of the Company's Predecessor Plans shall, upon the IPO
Date, be granted an Nonstatutory Stock Option to purchase Five Thousand (5,000)
shares of Common Stock on the terms and conditions set forth herein (the
"Initial Grant").

            (ii) After the IPO Date, each Eligible Director who is elected or
appointed to the Board less than six (6) from the prior annual meeting of the
stockholders of the Company (the "Annual Meeting"), shall receive a Nonstatutory
Stock Option to purchase Five Thousand (5,000) shares of Common Stock on the
terms and conditions set forth herein (the "Interim Grant"); provided, however,
that the Interim Grant shall be reduced to Two Thousand Five Hundred (2,500)
shares of Common Stock if the Eligible Director is elected or appointed to serve
on the Board six (6) months or more from the prior Annual Meeting.

      (b) Annual Grants. On the day following each Annual Meeting commencing
with the Annual Meeting in calendar year 2001, each person who is then an
Eligible Director automatically shall be granted an Annual Grant to Purchase
Five Thousand (5,000) shares of Common Stock on the terms and conditions set
forth herein.

      (c) Term. Each Non-Employee Director Option shall have a term of ten (10)
years from the date it is granted.

      (d) Exercise Price. The exercise price of each Non-Employee Director
Option shall be one hundred percent (100%) of the Fair Market Value of the stock
subject to the Non-Employee Director Option on the date of grant.
Notwithstanding the foregoing, a Non-Employee Director Option may be granted
with an exercise price lower than that set forth in the preceding sentence if
such Non-Employee Director Option is granted pursuant to an assumption or
substitution for another option in a manner satisfying the provisions of Section
424(a) of the Code.

      (e) Vesting. Non-Employee Director Options shall vest and become
exercisbable as follows:

            (i) Initial Grants shall vest in full on the day of the Company's
Annual Meeting immediately following the IPO Date; provided however, that the
Initial Grant shall terminate in the event the Eligible Director is not
providing service to the Company at the time of the commencement of such
Annual Meeting.

            (ii) Interim Grants shall vest in full on the day of the Company's
Annual Meeting next following the date of grant; provided, however, that the
Interim Grant shall terminate if the Eligible Director is not providing service
to the Company at the time of the commencement of such Annual Meeting.

                                       12
<PAGE>

            (iii) Annual Grants shall vest in full on the day of the Annual
Meeting next following the date of grant was made; provided, however, that
the Annual Grant shall terminate in the event the Eligible Director is not
providing service to the Company at the time of the commencement of such
Annual Meeting.

      (f) Consideration. The purchase price of stock acquired pursuant to a
Non-Employee Director Option may be paid, to the extent permitted by applicable
statutes and regulations, in any combination of (i) cash or check, (ii) delivery
to the Company of other Common Stock owned by the Director for at least six (6)
months; (iii) deferred payment or (iv) any other form of legal consideration
that may be acceptable to the Board and provided in the Non-Employee Director
Option Agreement; provided, however, that at any time that the Company is
incorporated in Delaware, payment of the Common Stock's "par value," as defined
in the Delaware Corporation Law, shall not be made by deferred payment.

      (g) Transferability. A Non-Employee Director Option shall be transferable
to the extent provided in the Non-Employee Director Option Agreement. If the
Non-Employee Director Option Agreement does not provide for transferability,
then the Non-Employee Director Option shall not be transferable except by will
or by the laws of descent and distribution and shall be exercisable during the
lifetime of the Eligible Director only by the Eligible Director. Notwithstanding
the foregoing, the Eligible Director may, by delivering written notice to the
Company, in a form satisfactory to the Company, designate a third party who, in
the event of the death of the Eligible Director, shall thereafter be entitled to
exercise the Non-Employee Director Option.

      (h) Termination of Continuous Service. In the event an Eligible Director's
Continuous Service terminates (other than upon the Eligible Director's death or
Disability), the Eligible Director may exercise his or her Non-Employee Director
Option (to the extent that the Eligible Director was entitled to exercise it as
of the date of termination) but only within such period of time ending on the
earlier of (i) the date six (6) months following the termination of the Eligible
Director's Continuous Service, or (ii) the expiration of the term of the
Non-Employee Director Option as set forth in the Non-Employee Director Option
Agreement. If, after termination, the Eligible Director does not exercise his or
her Non-Employee Director Option within the time specified herein, the
Non-Employee Director Option shall terminate.

      (i) Extension of Termination Date. If the exercise of the Non-Employee
Director Option following the termination of the Eligible Director's Continuous
Service (other than upon the Eligible Director's death or Disability) would be
prohibited at any time solely because the issuance of shares would violate the
registration requirements under the Securities Act, then the Non-Employee
Director Option shall terminate on the earlier of (i) the expiration of the term
of the Non-Employee Director Option set forth in subsection 7(c) or (ii) the
expiration of a period of three (3) months after the termination of the Eligible
Director's Continuous Service during which the exercise of the Non-Employee
Director Option would not violate such registration requirements.

      (j) Disability of Eligible Director. In the event an Eligible Director's
Continuous Service terminates as a result of the Eligible Director's Disability,
the Eligible Director may exercise his or her Non-Employee Director Option (to
the extent that the Eligible Director was

                                       13
<PAGE>

entitled to exercise it as of the date of termination), but only within such
period of time ending on the earlier of (i) the date twelve (12) months
following such termination or (ii) the expiration of the term of the
Non-Employee Director Option as set forth in the Non-Employee Director Option
Agreement. If, after termination, the Eligible Director does not exercise his or
her Non-Employee Director Option within the time specified herein, the
Non-Employee Director Option shall terminate.

      (k) Death of Eligible Director. In the event (i) an Eligible Director's
Continuous Service terminates as a result of the Eligible Director's death or
(ii) the Eligible Director dies within the six-month period after the
termination of the Eligible Director's Continuous Service for a reason other
than death, then the Non-Employee Director Option may be exercised (to the
extent the Eligible Director was entitled to exercise the Non-Employee Director
Option as of the date of death) by the Eligible Director's estate, by a person
who acquired the right to exercise the Non-Employee Director Option by bequest
or inheritance or by a person designated to exercise the Non-Employee Director
Option upon the Eligible Director's death, but only within the period ending on
the earlier of (1) the date eighteen (18) months following the date of death or
(2) the expiration of the term of such Non-Employee Director Option as set forth
in the Non-Employee Director Option Agreement. If, after death, the Non-Employee
Director Option is not exercised within the time specified herein, the
Non-Employee Director Option shall terminate.

8. PROVISIONS OF STOCK AWARDS OTHER THAN OPTIONS.

      (a) Stock Bonus Awards. Each stock bonus agreement shall be in such form
and shall contain such terms and conditions as the Board shall deem appropriate.
The terms and conditions of stock bonus agreements may change from time to time,
and the terms and conditions of separate stock bonus agreements need not be
identical, but each stock bonus agreement shall include (through incorporation
of provisions hereof by reference in the agreement or otherwise) the substance
of each of the following provisions:

            (i) Consideration. A stock bonus may be awarded in consideration for
past services actually rendered to the Company or an Affiliate for its benefit.

            (ii) Vesting. Shares of Common Stock awarded under the stock bonus
agreement may, but need not, be subject to a share reacquisition right in favor
of the Company in accordance with a vesting schedule to be determined by the
Board.

            (iii) Termination of Participant's Continuous Service. In the event
a Participant's Continuous Service terminates, the Company may reacquire any or
all of the shares of Common Stock held by the Participant which have not vested
as of the date of termination under the terms of the stock bonus agreement.

            (iv) Transferability. Rights to acquire shares of Common Stock under
the stock bonus agreement shall be transferable by the Participant only upon
such terms and conditions as are set forth in the stock bonus agreement, as the
Board shall determine in its discretion, so long as Common Stock awarded under
the stock bonus agreement remains subject to the terms of the stock bonus
agreement.

                                       14
<PAGE>

      (b) Restricted Stock Purchase Awards. Each restricted stock purchase
agreement shall be in such form and shall contain such terms and conditions as
the Board shall deem appropriate. The terms and conditions of the restricted
stock purchase agreements may change from time to time, and the terms and
conditions of separate restricted stock purchase agreements need not be
identical, but each restricted stock purchase agreement shall include (through
incorporation of provisions hereof by reference in the agreement or otherwise)
the substance of each of the following provisions:

            (i) Purchase Price. The purchase price under each restricted stock
purchase agreement shall be such amount as the Board shall determine and
designate in such restricted stock purchase agreement. The purchase price shall
not be less than eighty-five percent (85%) of the Common Stock's Fair Market
Value on the date such award is made or at the time the purchase is consummated.

            (ii) Consideration. The purchase price of Common Stock acquired
pursuant to the restricted stock purchase agreement shall be paid either: (i) in
cash at the time of purchase; (ii) at the discretion of the Board, according to
a deferred payment or other similar arrangement with the Participant; or (iii)
in any other form of legal consideration that may be acceptable to the Board in
its discretion; provided, however, that at any time that the Company is
incorporated in Delaware, then payment of the Common Stock's "par value," as
defined in the Delaware General Corporation Law, shall not be made by deferred
payment.

            (iii) Vesting. Shares of Common Stock acquired under the restricted
stock purchase agreement may, but need not, be subject to a share repurchase
option in favor of the Company in accordance with a vesting schedule to be
determined by the Board.

            (iv) Termination of Participant's Continuous Service. In the event a
Participant's Continuous Service terminates, the Company may repurchase or
otherwise reacquire any or all of the shares of Common Stock held by the
Participant which have not vested as of the date of termination under the terms
of the restricted stock purchase agreement.

            (v) Transferability. Rights to acquire shares of Common Stock under
the restricted stock purchase agreement shall be transferable by the Participant
only upon such terms and conditions as are set forth in the restricted stock
purchase agreement, as the Board shall determine in its discretion, so long as
Common Stock awarded under the restricted stock purchase agreement remains
subject to the terms of the restricted stock purchase agreement.

9. COVENANTS OF THE COMPANY.

      (a) Availability of Shares. During the terms of the Stock Awards, the
Company shall keep available at all times the number of shares of Common Stock
required to satisfy such Stock Awards.

      (b) Securities Law Compliance. The Company shall seek to obtain from each
regulatory commission or agency having jurisdiction over the Plan such authority
as may be required to grant Stock Awards and to issue and sell shares of Common
Stock upon exercise of the Stock Awards; provided, however, that this
undertaking shall not require the Company to register under the Securities Act
the Plan, any Stock Award or any Common Stock issued or

                                       15
<PAGE>

issuable pursuant to any such Stock Award. If, after reasonable efforts, the
Company is unable to obtain from any such regulatory commission or agency the
authority which counsel for the Company deems necessary for the lawful issuance
and sale of Common Stock under the Plan, the Company shall be relieved from any
liability for failure to issue and sell Common Stock upon exercise of such Stock
Awards unless and until such authority is obtained.

10. USE OF PROCEEDS FROM STOCK.

      Proceeds from the sale of Common Stock pursuant to Stock Awards shall
constitute general funds of the Company.

11. MISCELLANEOUS.

      (a) Acceleration of Exercisability and Vesting. The Board shall have the
power to accelerate the time at which a Stock Award may first be exercised or
the time during which a Stock Award or any part thereof will vest in accordance
with the Plan, notwithstanding the provisions in the Stock Award stating the
time at which it may first be exercised or the time during which it will vest.

      (b) Stockholder Rights. No Participant shall be deemed to be the holder
of, or to have any of the rights of a holder with respect to, any shares of
Common Stock subject to such Stock Award unless and until such Participant has
satisfied all requirements for exercise of the Stock Award pursuant to its
terms.

      (c) No Employment or other Service Rights. Nothing in the Plan or any
instrument executed or Stock Award granted pursuant thereto shall confer upon
any Participant any right to continue to serve the Company or an Affiliate in
the capacity in effect at the time the Stock Award was granted or shall affect
the right of the Company or an Affiliate to terminate (i) the employment of an
Employee with or without notice and with or without cause, (ii) the service of a
Consultant pursuant to the terms of such Consultant's agreement with the Company
or an Affiliate or (iii) the service of a Director pursuant to the Bylaws of the
Company or an Affiliate, and any applicable provisions of the corporate law of
the state in which the Company or the Affiliate is incorporated, as the case may
be.

      (d) Incentive Stock Option $100,000 Limitation. To the extent that the
aggregate Fair Market Value (determined at the time of grant) of Common Stock
with respect to which Incentive Stock Options are exercisable for the first time
by any Optionholder during any calendar year (under all plans of the Company and
its Affiliates) exceeds one hundred thousand dollars ($100,000), the Options or
portions thereof which exceed such limit (according to the order in which they
were granted) shall be treated as Nonstatutory Stock Options.

      (e) Investment Assurances. The Company may require a Participant, as a
condition of exercising or acquiring Common Stock under any Stock Award, (i) to
give written assurances satisfactory to the Company as to the Participant's
knowledge and experience in financial and business matters and/or to employ a
purchaser representative reasonably satisfactory to the Company who is
knowledgeable and experienced in financial and business matters and that he or
she is capable of evaluating, alone or together with the purchaser
representative, the merits and risks of exercising the Stock Award; and (ii) to
give written assurances satisfactory to

                                       16
<PAGE>

the Company stating that the Participant is acquiring Common Stock subject to
the Stock Award for the Participant's own account and not with any present
intention of selling or otherwise distributing the Common Stock. The foregoing
requirements, and any assurances given pursuant to such requirements, shall be
inoperative if (1) the issuance of the shares of Common Stock upon the exercise
or acquisition of Common Stock under the Stock Award has been registered under a
then currently effective registration statement under the Securities Act or (2)
as to any particular requirement, a determination is made by counsel for the
Company that such requirement need not be met in the circumstances under the
then applicable securities laws. The Company may, upon advice of counsel to the
Company, place legends on stock certificates issued under the Plan as such
counsel deems necessary or appropriate in order to comply with applicable
securities laws, including, but not limited to, legends restricting the transfer
of the Common Stock.

      (f) Withholding Obligations. To the extent provided by the terms of a
Stock Award Agreement, the Participant may satisfy any federal, state or local
tax withholding obligation relating to the exercise or acquisition of Common
Stock under a Stock Award by any of the following means (in addition to the
Company's right to withhold from any compensation paid to the Participant by the
Company) or by a combination of such means: (i) tendering a cash payment; (ii)
authorizing the Company to withhold shares of Common Stock from the shares of
Common Stock otherwise issuable to the Participant as a result of the exercise
or acquisition of Common Stock under the Stock Award, provided, however, that
the Company shall not be authorized to withheld shares of Common Stock in excess
if the minimum statutory rates for federal or state tax purposes including
payroll taxes; or (iii) delivering to the Company owned and unencumbered shares
of Common Stock.

12. ADJUSTMENTS UPON CHANGES IN COMMON STOCK.

      (a) Capitalization Adjustments. If any change is made in the Common Stock
subject to the Plan, or subject to any Stock Award, without the receipt of
consideration by the Company (through merger, consolidation, reorganization,
recapitalization, reincorporation, stock dividend, dividend in property other
than cash, stock split, liquidating dividend, combination of shares, exchange of
shares, change in corporate structure or other transaction not involving the
receipt of consideration by the Company), the Plan will be appropriately
adjusted in the class(es) and maximum number of securities subject to the Plan
pursuant to subsection 4(a) and the maximum number of securities subject to
award to any person pursuant to subsection 5(c), and the outstanding Stock
Awards will be appropriately adjusted in the class(es) and number of securities
and price per share of Common Stock subject to such outstanding Stock Awards.
The Board shall make such adjustments, and its determination shall be final,
binding and conclusive. (The conversion of any convertible securities of the
Company shall not be treated as a transaction "without receipt of consideration"
by the Company.)

      (b) Dissolution or Liquidation. In the event of a dissolution or
liquidation of the Company, then all outstanding Stock Awards shall terminate
immediately prior to such event.

      (c) Corporate Transaction. In the event of a Corporate Transaction, any
surviving corporation or acquiring corporation may assume any Stock Awards
outstanding under the Plan or may substitute similar stock awards (including an
award to acquire the same consideration

                                       17
<PAGE>

paid to the stockholders pursuant to the Corporate Transaction). In the event
any surviving corporation or acquiring corporation refuses to assume such Stock
Awards or to substitute similar stock awards for those outstanding under the
Plan, then with respect to Stock Awards held by Participants whose Continuous
Service has not terminated as of the effective date of the Corporate
Transaction, the vesting of such Stock Awards (and, if applicable, the time
during which such Stock Awards may be exercised) shall be accelerated in full,
and the Stock Awards shall terminate if not exercised (if applicable) at or
prior to such effective date. With respect to any other Stock Awards outstanding
under the Plan, such Stock Awards shall terminate if not exercised (if
applicable) prior the effective date of the Corporate Transaction.

      (d) Change in Control. If a Change in Control occurs and within thirteen
(13) months after the effective date of such Change in Control the Continuous
Service of a Participant terminates due to an involuntary termination (not
including death or Disability) without Cause or due to a voluntary termination
with Good Reason, then the vesting and exercisability of all Stock Awards held
by such Participant shall be accelerated in full.

13. AMENDMENT OF THE PLAN AND STOCK AWARDS.

      (a) Amendment of Plan. The Board at any time, and from time to time, may
amend the Plan. However, except as provided in Section 12 relating to
adjustments upon changes in Common Stock, no amendment shall be effective unless
approved by the stockholders of the Company to the extent stockholder approval
is necessary to satisfy the requirements of Section 422 of the Code, Rule 16b-3
or any Nasdaq or securities exchange listing requirements.

      (b) Stockholder Approval. The Board may, in its sole discretion, submit
any other amendment to the Plan for stockholder approval, including, but not
limited to, amendments to the Plan intended to satisfy the requirements of
Section 162(m) of the Code and the regulations thereunder regarding the
exclusion of performance-based compensation from the limit on corporate
deductibility of compensation paid to certain executive officers.

      (c) Contemplated Amendments. It is expressly contemplated that the Board
may amend the Plan in any respect the Board deems necessary or advisable to
provide eligible Employees with the maximum benefits provided or to be provided
under the provisions of the Code and the regulations promulgated thereunder
relating to Incentive Stock Options and/or to bring the Plan and/or Incentive
Stock Options granted under it into compliance therewith.

      (d) No Impairment of Rights. Rights under any Stock Award granted before
amendment of the Plan shall not be impaired by any amendment of the Plan unless
(i) the Company requests the consent of the Participant and (ii) the Participant
consents in writing.

      (e) Amendment of Stock Awards. The Board at any time, and from time to
time, may amend the terms of any one or more Stock Awards; provided, however,
that the rights under any Stock Award shall not be impaired by any such
amendment unless (i) the Company requests the consent of the Participant and
(ii) the Participant consents in writing.

14. TERMINATION OR SUSPENSION OF THE PLAN.

                                       18
<PAGE>

      (a) Plan Term. The Board may suspend or terminate the Plan at any time.
Unless sooner terminated, the Plan shall terminate on the day before the tenth
(10th) anniversary of the date the Plan is adopted by the Board or approved by
the stockholders of the Company, whichever is earlier. No Stock Awards may be
granted under the Plan while the Plan is suspended or after it is terminated.

      (b) No Impairment of Rights. Suspension or termination of the Plan shall
not impair rights and obligations under any Stock Award granted while the Plan
is in effect except with the written consent of the Participant.

15. EFFECTIVE DATE OF PLAN.

      The Plan shall become effective on the IPO Date, but no Stock Award shall
be exercised (or, in the case of a stock bonus, shall be granted) unless and
until the Plan has been approved by the stockholders of the Company, which
approval shall be within twelve (12) months before or after the date the Plan is
adopted by the Board.

16. CHOICE OF LAW.

      The law of the State of California shall govern all questions concerning
the construction, validity and interpretation of this Plan, without regard to
such state's conflict of laws rules.

                                       19
<PAGE>

                              PHARSIGHT CORPORATION
                           2000 EQUITY INCENTIVE PLAN

                             STOCK OPTION AGREEMENT
                  (INCENTIVE STOCK OPTION OR NONSTATUTORY STOCK OPTION)

      Pursuant to your Stock Option Grant Notice ("Grant Notice") and this Stock
Option Agreement, Pharsight Corporation (the "Company") has granted you an
option under its 2000 Equity Incentive (the "Plan") to purchase the number of
shares of the Company's Common Stock indicated in your Grant Notice at the
exercise price indicated in your Grant Notice. Defined terms not explicitly
defined in this Stock Option Agreement but defined in the Plan shall have the
same definitions as in the Plan.

      The details of your option are as follows:

I.    VESTING. Subject to the limitations contained herein, your option will
      vest as provided in your Grant Notice, provided that vesting will cease
      upon the termination of your Continuous Service.

II.   NUMBER OF SHARES AND EXERCISE PRICE. The number of shares of Common Stock
      subject to your option and your exercise price per share referenced in
      your Grant Notice may be adjusted from time to time for Capitalization
      Adjustments, as provided in the Plan.

III.  EXERCISE PRIOR TO VESTING ("EARLY EXERCISE"). If permitted in your Grant
      Notice (i.e., the "Exercise Schedule" indicates that "Early Exercise" of
      your option is permitted) and subject to the provisions of your option,
      you may elect at any time that is both (i) during the period of your
      Continuous Service and (ii) during the term of your option, to exercise
      all or part of your option, including the nonvested portion of your
      option; provided, however, that:

            a. a partial exercise of your option shall be deemed to cover first
vested shares of Common Stock and then the earliest vesting installment of
unvested shares of Common Stock;

            b. any shares of Common Stock so purchased from installments that
have not vested as of the date of exercise shall be subject to the purchase
option in favor of the Company as described in the Company's form of Early
Exercise Stock Purchase Agreement;

            c. you shall enter into the Company's form of Early Exercise Stock
Purchase Agreement with a vesting schedule that will result in the same vesting
as if no early exercise had occurred; and

            d. if your option is an incentive stock option, then, as provided in
the Plan, to the extent that the aggregate Fair Market Value (determined at the
time of grant) of the shares of Common Stock with respect to which your option
plus all other incentive stock options you hold

                                       20
<PAGE>

are exercisable for the first time by you during any calendar year (under all
plans of the Company and its Affiliates) exceeds one hundred thousand dollars
($100,000), your option(s) or portions thereof that exceed such limit (according
to the order in which they were granted) shall be treated as nonstatutory stock
options.

IV.   METHOD OF PAYMENT. Payment of the exercise price is due in full upon
      exercise of all or any part of your option. You may elect to make payment
      of the exercise price in cash or by check or in any other manner permitted
      by your Grant Notice, which may include one or more of the following:

            e. In the Company's sole discretion at the time your option is
exercised and provided that at the time of exercise the Common Stock is publicly
traded and quoted regularly in The Wall Street Journal, pursuant to a program
developed under Regulation T as promulgated by the Federal Reserve Board that,
prior to the issuance of Common Stock, results in either the receipt of cash (or
check) by the Company or the receipt of irrevocable instructions to pay the
aggregate exercise price to the Company from the sales proceeds.

            f. Provided that at the time of exercise the Common Stock is
publicly traded and quoted regularly in The Wall Street Journal, by delivery of
already-owned shares of Common Stock either that you have held for the period
required to avoid a charge to the Company's reported earnings (generally six
months) or that you did not acquire, directly or indirectly from the Company,
that are owned free and clear of any liens, claims, encumbrances or security
interests, and that are valued at Fair Market Value on the date of exercise.
"Delivery" for these purposes, in the sole discretion of the Company at the time
you exercise your option, shall include delivery to the Company of your
attestation of ownership of such shares of Common Stock in a form approved by
the Company. Notwithstanding the foregoing, you may not exercise your option by
tender to the Company of Common Stock to the extent such tender would violate
the provisions of any law, regulation or agreement restricting the redemption of
the Company's stock.

            g. Pursuant to the following deferred payment alternative:

            1)    Not less than one hundred percent (100%) of the aggregate
                  exercise price, plus accrued interest, shall be due four (4)
                  years from date of exercise or, at the Company's election,
                  upon termination of your Continuous Service.

            2)    Interest shall be compounded at least annually and shall be
                  charged at the minimum rate of interest necessary to avoid the
                  treatment as interest, under any applicable provisions of the
                  Code, of any portion of any amounts other than amounts stated
                  to be interest under the deferred payment arrangement.

            3)    At any time that the Company is incorporated in Delaware,
                  payment of the Common Stock's "par value," as defined in the
                  Delaware General Corporation Law, shall be made in cash and
                  not by deferred payment.

            4)    In order to elect the deferred payment alternative, you must,
                  as a part of your written notice of exercise, give notice of
                  the election of this payment

                                       21
<PAGE>

                  alternative and, in order to secure the payment of the
                  deferred exercise price to the Company hereunder, if the
                  Company so requests, you must tender to the Company a
                  promissory note and a security agreement covering the
                  purchased shares of Common Stock, both in form and substance
                  satisfactory to the Company, or such other or additional
                  documentation as the Company may request.

V.    WHOLE SHARES. You may exercise your option only for whole shares of Common
      Stock.

VI.   SECURITIES LAW COMPLIANCE. Notwithstanding anything to the contrary
      contained herein, you may not exercise your option unless the shares of
      Common Stock issuable upon such exercise are then registered under the
      Securities Act or, if such shares of Common Stock are not then so
      registered, the Company has determined that such exercise and issuance
      would be exempt from the registration requirements of the Securities Act.
      The exercise of your option must also comply with other applicable laws
      and regulations governing your option, and you may not exercise your
      option if the Company determines that such exercise would not be in
      material compliance with such laws and regulations.

VII.  TERM. You may not exercise your option before the commencement of its term
      or after its term expires. The term of your option commences on the Date
      of Grant and expires upon the earliest of the following:

            h. three (3) months after the termination of your Continuous Service
for any reason other than your Disability or death, provided that if during any
part of such three- (3-) month period your option is not exercisable solely
because of the condition set forth in the preceding paragraph relating to
"Securities Law Compliance," your option shall not expire until the earlier of
the Expiration Date or until it shall have been exercisable for an aggregate
period of three (3) months after the termination of your Continuous Service;

            i. twelve (12) months after the termination of your Continuous
Service due to your Disability;

            j. eighteen (18) months after your death if you die either during
your Continuous Service or within three (3) months after your Continuous Service
terminates;

            k. the Expiration Date indicated in your Grant Notice; or

            l. the day before the tenth (10th) anniversary of the Date of Grant.

      If your option is an incentive stock option, note that, to obtain the
federal income tax advantages associated with an "incentive stock option," the
Code requires that at all times beginning on the date of grant of your option
and ending on the day three (3) months before the date of your option's
exercise, you must be an employee of the Company or an Affiliate, except in the
event of your death or Disability. The Company has provided for extended
exercisability of your option under certain circumstances for your benefit but
cannot guarantee that your option will necessarily be treated as an "incentive
stock option" if you continue to provide services to

                                       22
<PAGE>

the Company or an Affiliate as a Consultant or Director after your employment
terminates or if you otherwise exercise your option more than three (3) months
after the date your employment terminates.

VIII. EXERCISE.

            m. You may exercise the vested portion of your option (and the
unvested portion of your option if your Grant Notice so permits) during its term
by delivering a Notice of Exercise (in a form designated by the Company)
together with the exercise price to the Secretary of the Company, or to such
other person as the Company may designate, during regular business hours,
together with such additional documents as the Company may then require.

            n. By exercising your option you agree that, as a condition to any
exercise of your option, the Company may require you to enter into an
arrangement providing for the payment by you to the Company of any tax
withholding obligation of the Company arising by reason of (1) the exercise of
your option, (2) the lapse of any substantial risk of forfeiture to which the
shares of Common Stock are subject at the time of exercise, or (3) the
disposition of shares of Common Stock acquired upon such exercise.

            o. If your option is an incentive stock option, by exercising your
option you agree that you will notify the Company in writing within fifteen (15)
days after the date of any disposition of any of the shares of the Common Stock
issued upon exercise of your option that occurs within two (2) years after the
date of your option grant or within one (1) year after such shares of Common
Stock are transferred upon exercise of your option.

            p. By exercising your option you agree that the Company (or a
representative of the underwriter(s)) may, in connection with the first
underwritten registration of the offering of any securities of the Company under
the Securities Act, require that you not sell, dispose of, transfer, make any
short sale of, grant any option for the purchase of, or enter into any hedging
or similar transaction with the same economic effect as a sale, any shares of
Common Stock or other securities of the Company held by you, for a period of
time specified by the underwriter(s) (not to exceed one hundred eighty (180)
days) following the effective date of the registration statement of the Company
filed under the Securities Act. You further agree to execute and deliver such
other agreements as may be reasonably requested by the Company and/or the
underwriter(s) that are consistent with the foregoing or that are necessary to
give further effect thereto. In order to enforce the foregoing covenant, the
Company may impose stop-transfer instructions with respect to your shares of
Common Stock until the end of such period.

IX.   TRANSFERABILITY. Your option is not transferable, except by will or by the
      laws of descent and distribution, and is exercisable during your life only
      by you. Notwithstanding the foregoing, by delivering written notice to the
      Company, in a form satisfactory to the Company, you may designate a third
      party who, in the event of your death, shall thereafter be entitled to
      exercise your option.

X.    RIGHT OF REPURCHASE. Unvested shares that are received upon an early
      exercise of your option are subject to any right of repurchase that may be
      described in the form of

                                       23
<PAGE>

      Early Exercise Stock Purchase Agreement by which you acquire shares of
      Common Stock pursuant to the early exercise of your option.

XI.   OPTION NOT A SERVICE CONTRACT. Your option is not an employment or service
      contract, and nothing in your option shall be deemed to create in any way
      whatsoever any obligation on your part to continue in the employ of the
      Company or an Affiliate, or of the Company or an Affiliate to continue
      your employment. In addition, nothing in your option shall obligate the
      Company or an Affiliate, their respective stockholders, Boards of
      Directors, Officers or Employees to continue any relationship that you
      might have as a Director or Consultant for the Company or an Affiliate.

XII.  WITHHOLDING OBLIGATIONS.

            q. At the time you exercise your option, in whole or in part, or at
any time thereafter as requested by the Company, you hereby authorize
withholding from payroll and any other amounts payable to you, and otherwise
agree to make adequate provision for (including by means of a "same day sale"
pursuant to a program developed under Regulation T as promulgated by the Federal
Reserve Board to the extent permitted by the Company), any sums required to
satisfy the federal, state, local and foreign tax withholding obligations of the
Company or an Affiliate, if any, which arise in connection with your option.

            r. Upon your request and subject to approval by the Company, in its
sole discretion, and compliance with any applicable conditions or restrictions
of law, the Company may withhold from fully vested shares of Common Stock
otherwise issuable to you upon the exercise of your option a number of whole
shares of Common Stock having a Fair Market Value, determined by the Company as
of the date of exercise, not in excess of the minimum amount of tax required to
be withheld by law. If the date of determination of any tax withholding
obligation is deferred to a date later than the date of exercise of your option,
share withholding pursuant to the preceding sentence shall not be permitted
unless you make a proper and timely election under Section 83(b) of the Code,
covering the aggregate number of shares of Common Stock acquired upon such
exercise with respect to which such determination is otherwise deferred, to
accelerate the determination of such tax withholding obligation to the date of
exercise of your option. Notwithstanding the filing of such election, shares of
Common Stock shall be withheld solely from fully vested shares of Common Stock
determined as of the date of exercise of your option that are otherwise issuable
to you upon such exercise. Any adverse consequences to you arising in connection
with such share withholding procedure shall be your sole responsibility.

            s. You may not exercise your option unless the tax withholding
obligations of the Company and/or any Affiliate are satisfied. Accordingly, you
may not be able to exercise your option when desired even though your option is
vested, and the Company shall have no obligation to issue a certificate for such
shares of Common Stock or release such shares of Common Stock from any escrow
provided for herein.

XIII. NOTICES. Any notices provided for in your option or the Plan shall be
      given in writing and shall be deemed effectively given upon receipt or, in
      the case of notices delivered by

                                       24
<PAGE>

      mail by the Company to you, five (5) days after deposit in the United
      States mail, postage prepaid, addressed to you at the last address you
      provided to the Company.

XIV.  GOVERNING PLAN DOCUMENT. Your option is subject to all the provisions of
      the Plan, the provisions of which are hereby made a part of your option,
      and is further subject to all interpretations, amendments, rules and
      regulations which may from time to time be promulgated and adopted
      pursuant to the Plan. In the event of any conflict between the provisions
      of your option and those of the Plan, the provisions of the Plan shall
      control.

                                       25
<PAGE>

                              PHARSIGHT CORPORATION
                           2000 EQUITY INCENTIVE PLAN

                     NON-EMPLOYEE DIRECTOR OPTION AGREEMENT

      Pursuant to your Non-Employee Director Option Grant Notice ("Grant
Notice") and this Non-Employee Director Option Agreement, Pharsight Corporation
(the "Company") has granted you an option under its 2000 Equity Incentive Plan
(the "Plan") to purchase the number of shares of the Company's Common Stock
indicated in your Grant Notice at the exercise price indicated in your Grant
Notice. Defined terms not explicitly defined in this Non-Employee Director
Option Agreement but defined in the Plan shall have the same definitions as in
the Plan.

      The details of your option are as follows:

XV.   VESTING. Subject to the limitations contained herein, your option will
      vest as provided in your Grant Notice, provided that vesting will cease
      upon the termination of your Continuous Service.

XVI.  NUMBER OF SHARES AND EXERCISE PRICE. The number of shares of Common Stock
      subject to your option and your exercise price per share referenced in
      your Grant Notice may be adjusted from time to time for Capitalization
      Adjustments, as provided in the Plan.

XVII. EXERCISE PRIOR TO VESTING ("EARLY EXERCISE"). If permitted in your Grant
      Notice (i.e., the "Exercise Schedule" indicates that "Early Exercise" of
      your option is permitted) and subject to the provisions of your option,
      you may elect at any time that is both (i) during the period of your
      Continuous Service and (ii) during the term of your option, to exercise
      all or part of your option, including the nonvested portion of your
      option; provided, however, that:

            t. a partial exercise of your option shall be deemed to cover first
vested shares of Common Stock and then the earliest vesting installment of
unvested shares of Common Stock;

            u. any shares of Common Stock so purchased from installments that
have not vested as of the date of exercise shall be subject to the purchase
option in favor of the Company as described in the Company's form of Early
Exercise Stock Purchase Agreement; and

                                       26
<PAGE>

            v. you shall enter into the Company's form of Early Exercise Stock
Purchase Agreement with a vesting schedule that will result in the same vesting
as if no early exercise had occurred.

XVIII. METHOD OF PAYMENT. Payment of the exercise price is due in full upon
      exercise of all or any part of your option. You may elect to make payment
      of the exercise price in cash or by check or in any other manner permitted
      by your Grant Notice, which may include one or more of the following:

            w. In the Company's sole discretion at the time your option is
exercised and provided that at the time of exercise the Common Stock is publicly
traded and quoted regularly in The Wall Street Journal, pursuant to a program
developed under Regulation T as promulgated by the Federal Reserve Board that,
prior to the issuance of Common Stock, results in either the receipt of cash (or
check) by the Company or the receipt of irrevocable instructions to pay the
aggregate exercise price to the Company from the sales proceeds.

            x. Provided that at the time of exercise the Common Stock is
publicly traded and quoted regularly in The Wall Street Journal, by delivery of
already-owned shares of Common Stock either that you have held for the period
required to avoid a charge to the Company's reported earnings (generally six
months) or that you did not acquire, directly or indirectly from the Company,
that are owned free and clear of any liens, claims, encumbrances or security
interests, and that are valued at Fair Market Value on the date of exercise.
"Delivery" for these purposes, in the sole discretion of the Company at the time
you exercise your option, shall include delivery to the Company of your
attestation of ownership of such shares of Common Stock in a form approved by
the Company. Notwithstanding the foregoing, you may not exercise your option by
tender to the Company of Common Stock to the extent such tender would violate
the provisions of any law, regulation or agreement restricting the redemption of
the Company's stock.

            y. Pursuant to the following deferred payment alternative:

            1)    Not less than one hundred percent (100%) of the aggregate
                  exercise price, plus accrued interest, shall be due four (4)
                  years from the date of exercise, at the Company's election,
                  upon termination of your Continuous Service.

            2)    Interest shall be compounded at least annually and shall be
                  charged at the minimum rate of interest necessary to avoid the
                  treatment as interest, under any applicable provisions of the
                  Code, of any portion of any amounts other than amounts stated
                  to be interest under the deferred payment arrangement.

            3)    At any time that the Company is incorporated in Delaware,
                  payment of the Common Stock's "par value," as defined in the
                  Delaware General Corporation Law, shall be made in cash and
                  not be deferred payment.

            4)    In order to elect the deferred payment alternative, you must,
                  as a part of your written notice of exercise, give notice of
                  the election of this

                                       27
<PAGE>

                  payment alternative and, in order to secure the payment of the
                  deferred exercise price to the Company hereunder, if the
                  Company so requests, you must tender to the Company a
                  promissory note and a security agreement covering the
                  purchased shares of Common Stock, both in form and substance
                  satisfactory to the Company, or such other or additional
                  documentation as the Company may request.

XIX.  WHOLE SHARES. You may exercise your option only for whole shares of Common
      Stock.

XX.   SECURITIES LAW COMPLIANCE. Notwithstanding anything to the contrary
      contained herein, you may not exercise your option unless the shares of
      Common Stock issuable upon such exercise are then registered under the
      Securities Act or, if such shares of Common Stock are not then so
      registered, the Company has determined that such exercise and issuance
      would be exempt from the registration requirements of the Securities Act.
      The exercise of your option must also comply with other applicable laws
      and regulations governing your option, and you may not exercise your
      option if the Company determines that such exercise would not be in
      material compliance with such laws and regulations.

XXI.  TERM. You may not exercise your option before the commencement of its term
      or after its term expires. The term of your option commences on the Date
      of Grant and expires upon the earliest of the following:

            z. Six (6) months after the termination of your Continuous Service
for any reason other than your Disability or death, provided that if during any
part of such six (6) month period your option is not exercisable solely because
of the condition set forth in the preceding paragraph relating to "Securities
Law Compliance," your option shall not expire until the earlier of the
Expiration Date or until it shall have been exercisable for an aggregate period
of three (3) months after the termination of your Continuous Service;

            aa. twelve (12) months after the termination of your Continuous
Service due to your Disability;

            bb. eighteen (18) months after your death if you die either during
your Continuous Service or within three (3) months after your Continuous Service
terminates;

            cc. the Expiration Date indicated in your Grant Notice; or

            dd. the day before the tenth (10th) anniversary of the Date of
Grant.

XXII. EXERCISE.

            ee. You may exercise the vested portion of your option (and the
unvested portion of your option if your Grant Notice so permits) during its term
by delivering a Notice of Exercise (in a form designated by the Company)
together with the exercise price to the Secretary of the Company, or to such
other person as the Company may designate, during regular business hours,
together with such additional documents as the Company may then require.

                                       28
<PAGE>

            ff. By exercising your option you agree that, as a condition to any
exercise of your option, the Company may require you to enter into an
arrangement providing for the payment by you to the Company of any tax
withholding obligation of the Company arising by reason of (1) the exercise of
your option, (2) the lapse of any substantial risk of forfeiture to which the
shares of Common Stock are subject at the time of exercise, or (3) the
disposition of shares of Common Stock acquired upon such exercise.

            gg. By exercising your option you agree that the Company (or a
representative of the underwriter(s)) may, in connection with the first
underwritten registration of the offering of any securities of the Company under
the Securities Act, require that you not sell, dispose of, transfer, make any
short sale of, grant any option for the purchase of, or enter into any hedging
or similar transaction with the same economic effect as a sale, any shares of
Common Stock or other securities of the Company held by you, for a period of
time specified by the underwriter(s) (not to exceed one hundred eighty (180)
days) following the effective date of the registration statement of the Company
filed under the Securities Act. You further agree to execute and deliver such
other agreements as may be reasonably requested by the Company and/or the
underwriter(s) that are consistent with the foregoing or that are necessary to
give further effect thereto. In order to enforce the foregoing covenant, the
Company may impose stop-transfer instructions with respect to your shares of
Common Stock until the end of such period.

      9. TRANSFERABILITY. Your option is not transferable, except by will or by
the laws of descent and distribution, and is exercisable during your life only
by you. Notwithstanding the foregoing, by delivering written notice to the
Company, in a form satisfactory to the Company, you may designate a third party
who, in the event of your death, shall thereafter be entitled to exercise your
option.

      10. RIGHT OF REPURCHASE. Unvested shares that are received upon an early
exercise of your option are subject to any right of repurchase that may be
described in the form of Early Exercise Stock Purchase Agreement by which you
acquire shares of Common Stock of the Company pursuant to the early exercise of
your option.

XXIII.OPTION NOT A SERVICE CONTRACT. Your option is not an employment or service
      contract, and nothing in your option shall be deemed to create in any way
      whatsoever any obligation on your part to continue in the employ of the
      Company or an Affiliate, or of the Company or an Affiliate to continue
      your employment. In addition, nothing in your option shall obligate the
      Company or an Affiliate, their respective stockholders, Boards of
      Directors, Officers or Employees to continue any relationship that you
      might have as a Director or Consultant for the Company or an Affiliate.

XXIV. WITHHOLDING OBLIGATIONS.

            a. At the time you exercise your option, in whole or in part, or at
any time thereafter as requested by the Company, you hereby authorize
withholding from payroll and any other amounts payable to you, and otherwise
agree to make adequate provision for (including by means of a "same day sale"
pursuant to a program developed under Regulation T as promulgated by the Federal
Reserve Board to the extent permitted by the Company), any sums required to

                                       29
<PAGE>

satisfy the federal, state, local and foreign tax withholding obligations of the
Company or an Affiliate, if any, which arise in connection with your option.

            b. Upon your request and subject to approval by the Company, in its
sole discretion, and compliance with any applicable conditions or restrictions
of law, the Company may withhold from fully vested shares of Common Stock
otherwise issuable to you upon the exercise of your option a number of whole
shares of Common Stock having a Fair Market Value, determined by the Company as
of the date of exercise, not in excess of the minimum amount of tax required to
be withheld by law. If the date of determination of any tax withholding
obligation is deferred to a date later than the date of exercise of your option,
share withholding pursuant to the preceding sentence shall not be permitted
unless you make a proper and timely election under Section 83(b) of the Code,
covering the aggregate number of shares of Common Stock acquired upon such
exercise with respect to which such determination is otherwise deferred, to
accelerate the determination of such tax withholding obligation to the date of
exercise of your option. Notwithstanding the filing of such election, shares of
Common Stock shall be withheld solely from fully vested shares of Common Stock
determined as of the date of exercise of your option that are otherwise issuable
to you upon such exercise. Any adverse consequences to you arising in connection
with such share withholding procedure shall be your sole responsibility.

            c. You may not exercise your option unless the tax withholding
obligations of the Company and/or any Affiliate are satisfied. Accordingly, you
may not be able to exercise your option when desired even though your option is
vested, and the Company shall have no obligation to issue a certificate for such
shares of Common Stock or release such shares of Common Stock from any escrow
provided for herein.

XXV.  NOTICES. Any notices provided for in your option or the Plan shall be
      given in writing and shall be deemed effectively given upon receipt or, in
      the case of notices delivered by mail by the Company to you, five (5) days
      after deposit in the United States mail, postage prepaid, addressed to you
      at the last address you provided to the Company.

      11. GOVERNING PLAN DOCUMENT. Your option is subject to all the provisions
of the Plan, the provisions of which are hereby made a part of your option, and
is further subject to all interpretations, amendments, rules and regulations
which may from time to time be promulgated and adopted pursuant to the Plan. In
the event of any conflict between the provisions of your option and those of the
Plan, the provisions of the Plan shall control.

                                       30
<PAGE>

                              PHARSIGHT CORPORATION
                            STOCK OPTION GRANT NOTICE
                          (2000 EQUITY INCENTIVE PLAN)

Pharsight Corporation (the "Company"), pursuant to its 2000 Equity Incentive
Plan (the "Plan"), hereby grants to Optionholder an option to purchase the
number of shares of the Company's Common Stock set forth below. This option is
subject to all of the terms and conditions as set forth herein and in the Stock
Option Agreement, the Plan and the Notice of Exercise, all of which are attached
hereto and incorporated herein in their entirety.

Optionholder:                         _________________________________________
Date of Grant:                        _________________________________________
Vesting Commencement Date:            _________________________________________
Number of Shares Subject to Option:   _________________________________________
Exercise Price (Per Share):           _________________________________________
Total Exercise Price:                 _________________________________________
Expiration Date:                      _________________________________________

Type of Grant:       |_| Incentive Stock Option    |_| Nonstatutory Stock Option

Exercise Schedule:   |_| Same as Vesting Schedule  |_| Early Exercise Permitted

Vesting Schedule:    1/4th of the  shares  vest one  year  after  the
Vesting Commencement
Date.                1/48th of the shares vest monthly thereafter over the next
                     three years.

Payment:             By one or a combination of the following items (described
                     in the Stock Option Agreement):

                     By cash or check
                     Pursuant to a Regulation T Program if the Shares are
                     publicly traded By delivery of already-owned shares if the
                     Shares are publicly traded [By deferred payment]

Additional Terms/Acknowledgements: The undersigned Optionholder acknowledges
receipt of, and understands and agrees to, this Grant Notice, the Stock Option
Agreement and the Plan. Optionholder further acknowledges that as of the Date of
Grant, this Grant Notice, the Stock Option Agreement and the Plan set forth the
entire understanding between Optionholder and the Company regarding the
acquisition of stock in the Company and supersede all prior oral and written
agreements on that subject with the exception of (i) options previously granted
and delivered to Optionholder under the Plan, and (ii) the following agreements
only:

      OTHER AGREEMENTS:       _________________________________________________
                              _________________________________________________

                                       31
<PAGE>

PHARSIGHT CORPORATION                    OPTIONHOLDER:

By___________________________________    By_____________________________________
             Signature                                Signature

Title:_______________________________    Date:__________________________________

Date:________________________________

ATTACHMENTS: Stock Option Agreement, 2000 Equity Incentive Plan and Notice of
Exercise

                                       32
<PAGE>

                                    Exhibit I

                             STOCK OPTION AGREEMENT

                                       33
<PAGE>

                                   Exhibit II

                           2000 EQUITY INCENTIVE PLAN

                                       34
<PAGE>

                                   Exhibit III

                               NOTICE OF EXERCISE

                                       35
<PAGE>

                               NOTICE OF EXERCISE

Pharsight Corporation
800 West El Camino Real, Suite 200
Mountain View, California  94040             Date of Exercise: _______________

Ladies and Gentlemen:

      This constitutes notice under my stock option that I elect to purchase the
number of shares for the price set forth below.

      Type of option (check one):   Incentive  |_|    Nonstatutory  |_|

      Stock option dated:           _______________

      Number of shares as
      to which option is
      exercised:                    _______________

      Certificates to be
      issued in name of:            _______________

      Total exercise price:         $______________

      Cash payment delivered
      herewith:                     $______________

      Value of ________ shares of
      Pharsight Corporation common
      stock delivered herewith:     $______________]

      By this exercise, I agree (i) to provide such additional documents as you
may require pursuant to the terms of the 2000 Equity Incentive Plan, (ii) to
provide for the payment by me to you (in the manner designated by you) of your
withholding obligation, if any, relating to the exercise of this option, and
(iii) if this exercise relates to an incentive stock option, to notify you in
writing within fifteen (15) days after the date of any disposition of any of the
shares of Common Stock issued upon exercise of this option that occurs within
two (2) years after the date of grant of this option or within one (1) year
after such shares of Common Stock are issued upon exercise of this option.

      I hereby make the following certifications and representations with
respect to the number of shares of Common Stock of the Company listed above (the
"Shares"), which are being acquired by me for my own account upon exercise of
the Option as set forth above:

      I further acknowledge that I will not be able to resell the Shares for at
least ninety (90) days after the stock of the Company becomes publicly traded
(i.e., subject to the reporting

                                       36
<PAGE>

requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934)
under Rule 701 and that more restrictive conditions apply to affiliates of the
Company under Rule 144.

      I further acknowledge that all certificates representing any of the Shares
subject to the provisions of the Option shall have endorsed thereon appropriate
legends reflecting the foregoing limitations, as well as any legends reflecting
restrictions pursuant to the Company's Articles of Incorporation, Bylaws and/or
applicable securities laws.

      I further agree that, if required by the Company (or a representative of
the underwriters) in connection with the first underwritten registration of the
offering of any securities of the Company under the Securities Act, I will not
sell, dispose of, transfer, make any short sale of, grant any option for the
purchase of, or enter into any hedging or similar transaction with the same
economic effect as a sale, any Shares or other securities of the Company held by
me, for a period of time specified by the underwriter(s) (not to exceed one
hundred eighty (180) days) following the effective date of the registration
statement of the Company filed under the Securities Act. I further agree to
execute and deliver such other agreements as may be reasonably requested by the
Company and/or the underwriter(s) that are consistent with the foregoing or that
are necessary to give further effect thereto. In order to enforce the foregoing
covenant, the Company may impose stop-transfer instructions with respect to my
Shares until the end of such period.

                                          Very truly yours,

                                          _____________________________________

                                       37
<PAGE>

                              PHARSIGHT CORPORATION
                    NON-EMPLOYEE DIRECTOR OPTION GRANT NOTICE
                                  INITIAL GRANT
                           2000 EQUITY INCENTIVE PLAN

Pharsight Corporation (the "Company"), pursuant to its 2000 Equity Incentive
Plan (the "Plan"), hereby grants to Optionholder an option to purchase the
number of shares of the Company's Common Stock set forth below. This option is
subject to all of the terms and conditions as set forth herein and in the
Non-Employee Director Option Agreement, the Plan and the Notice of Exercise, all
of which are attached hereto and incorporated herein in their entirety.

Optionholder:
                                       ----------------------------------------
Date of Grant:
                                       ----------------------------------------
Vesting Commencement Date:
                                       ----------------------------------------
Number of Shares Subject to Option:    Five Thousand (5,000)
                                       ----------------------------------------
Exercise Price (Per Share):
                                       ----------------------------------------
Total Exercise Price:
                                       ----------------------------------------
Expiration Date:                       Ten (10) years from Date of Grant

TYPE OF GRANT:       Nonstatutory Stock Option (Initial Grant)

EXERCISE SCHEDULE:   / /  Same as Vesting    / /  Early Exercise
                          Schedule                Permitted

VESTING SCHEDULE:    100% of the shares vest one year after the Vesting
                     Commencement Date.

PAYMENT:             By one or a combination of the following items (described
                     in the Non-Employee Director Option Agreement):

                                By cash or check
                                Pursuant to a Regulation T Program if the Common
                                Stock is publicly traded By delivery of
                                already-owned shares if the Common Stock is
                                publicly traded [By deferred payment]

ADDITIONAL TERMS/ACKNOWLEDGEMENTS: The undersigned Optionholder acknowledges
receipt of, and understands and agrees to, this Grant Notice, the Non-Employee
Director Option Agreement and the Plan. Optionholder further acknowledges that
as of the Date of Grant, this Grant Notice, the Non-Employee Director Option
Agreement and the Plan set forth the entire understanding between Optionholder
and the Company regarding the acquisition of stock in the Company and supersede
all prior oral and written agreements on that subject with the exception of (i)
stock awards previously granted and delivered to Optionholder under the Plan or
a Predecessor Plan, and (ii) the following agreements only:

         OTHER AGREEMENTS:
                                            -----------------------------------
                                            -----------------------------------

PHARSIGHT CORPORATION                                         OPTIONHOLDER:

By:
   ------------------------------------     -----------------------------------
            Signature                                      Signature

Title:                                      Date:
      ---------------------------------          ------------------------------

Date:
     ----------------------------------

ATTACHMENTS: Non-Employee Director Option Agreement, 2000 Equity Incentive Plan
and Notice of Exercise

<PAGE>

                                    EXHIBIT I

                     NON-EMPLOYEE DIRECTOR OPTION AGREEMENT

<PAGE>

                                   EXHIBIT II

                           2000 EQUITY INCENTIVE PLAN

<PAGE>

                                   EXHIBIT III

                               NOTICE OF EXERCISE

<PAGE>

                              PHARSIGHT CORPORATION
                    NON-EMPLOYEE DIRECTOR OPTION GRANT NOTICE
                                  ANNUAL GRANT
                           2000 EQUITY INCENTIVE PLAN

Pharsight Corporation (the "Company"), pursuant to its 2000 Equity Incentive
Plan (the "Plan"), hereby grants to Optionholder an option to purchase the
number of shares of the Company's Common Stock set forth below. This option is
subject to all of the terms and conditions as set forth herein and in the
Non-Employee Director Option Agreement, the Plan and the Notice of Exercise, all
of which are attached hereto and incorporated herein in their entirety.

Optionholder:
                                       ----------------------------------------
Date of Grant:
                                       ----------------------------------------
Vesting Commencement Date:
                                       ----------------------------------------
Number of Shares Subject to Option:    Five thousand (5,000)
                                       ----------------------------------------
Exercise Price (Per Share):
                                       ----------------------------------------
Total Exercise Price:
                                       ----------------------------------------
Expiration Date:                       Ten (10) years from Date of Grant

TYPE OF GRANT:       Nonstatutory Stock Option (Annual Grant)

EXERCISE SCHEDULE:   / /  Same as Vesting    / /  Early Exercise
                          Schedule                Permitted

VESTING SCHEDULE:    100% of the shares vest one year after the Vesting
                     Commencement Date.

PAYMENT:             By one or a combination of the following items (described
                     in the Non-Employee Director Option Agreement):

                                By cash or check
                                Pursuant to a Regulation T Program if the Common
                                Stock is publicly traded By delivery of
                                already-owned shares if the Common Stock is
                                publicly traded [By deferred payment]

ADDITIONAL TERMS/ACKNOWLEDGEMENTS: The undersigned Optionholder acknowledges
receipt of, and understands and agrees to, this Grant Notice, the Non-Employee
Director Option Agreement and the Plan. Optionholder further acknowledges that
as of the Date of Grant, this Grant Notice, the Non-Employee Director Option
Agreement and the Plan set forth the entire understanding between Optionholder
and the Company regarding the acquisition of stock in the Company and supersede
all prior oral and written agreements on that subject with the exception of (i)
stock awards previously granted and delivered to Optionholder under the Plan or
a Predecessor Plan, and (ii) the following agreements only:

         OTHER AGREEMENTS:
                                            -----------------------------------
                                            -----------------------------------

PHARSIGHT CORPORATION                                         OPTIONHOLDER:

By:
   ------------------------------------     -----------------------------------
            Signature                                      Signature

Title:                                      Date:
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ATTACHMENTS: Non-Employee Director Option Agreement, 2000 Equity Incentive Plan
and Notice of Exercise

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                                    EXHIBIT I

                     NON-EMPLOYEE DIRECTOR OPTION AGREEMENT

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                                   EXHIBIT II

                           2000 EQUITY INCENTIVE PLAN

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                                   EXHIBIT III

                               NOTICE OF EXERCISE<PAGE>

                                                                   Exhibit 10.20
                              PHARSIGHT CORPORATION

                        2000 EMPLOYEE STOCK PURCHASE PLAN

                              Adopted April 7, 2000
                 Approved by the Stockholders on May __, 2000
                 Effective Date: Date of Initial Public Offering

1. PURPOSE.

      (a) The purpose of this 2000 Employee Stock Purchase Plan (the "Plan") is
to provide a means by which employees of Pharsight Corporation, a Delaware
corporation (the "Company"), and its Affiliates, as defined in subparagraph
1(b), which are designated as provided in subparagraph 2(b), may be given an
opportunity to purchase stock of the Company.

      (b) The word "Affiliate" as used in the Plan means any parent corporation
or subsidiary corporation of the Company, as those terms are defined in Sections
424(e) and (f), respectively, of the Internal Revenue Code of 1986, as amended
(the "Code").

      (c) The Company, by means of the Plan, seeks to retain the services of its
employees, to secure and retain the services of new employees, and to provide
incentives for such persons to exert maximum efforts for the success of the
Company.

      (d) The Company intends that the rights to purchase stock of the Company
granted under the Plan be considered options issued under an "employee stock
purchase plan" as that term is defined in Section 423(b) of the Code.

2. ADMINISTRATION.

      (a) The Plan shall be administered by the Board of Directors (the "Board")
of the Company unless and until the Board delegates administration to a
committee as provided in subparagraph 2(c). Whether or not the Board has
delegated administration the Board shall have the final power to determine all
questions of policy and expediency that may arise in the administration of the
Plan.

      (b) The Board shall have the power, subject to, and within the limitations
of, the express provisions of the Plan:

            (i) To determine when and how rights to purchase stock of the
Company shall be granted and the provisions of each offering of such rights
(which need not be identical).

            (ii) To designate from time to time which Affiliates of the Company
shall be eligible to participate in the Plan.

            (iii) To construe and interpret the Plan and rights granted under
it, and to establish, amend and revoke rules and regulations for its
administration. The Board, in the

                                       1.
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exercise of this power, may correct any defect, omission or inconsistency in the
Plan, in a manner and to the extent it shall deem necessary or expedient to make
the Plan fully effective.

            (iv) To amend the Plan as provided in paragraph 13.

            (v) Generally, to exercise such powers and to perform such acts as
the Board or the Committee deems necessary or expedient to promote the best
interests of the Company and its Affiliates and to carry out the intent that the
Plan be treated as an "employee stock purchase plan" within the meaning of
Section 423 of the Code.

      (c) The Board may delegate administration of the Plan to a committee
composed of not fewer than two (2) members of the Board (the "Committee"). If
administration is delegated to a Committee, the Committee shall have, in
connection with the administration of the Plan, the powers theretofore possessed
by the Board, subject, however, to such resolutions, not inconsistent with the
provisions of the Plan, as may be adopted from time to time by the Board. The
Board may abolish the Committee at any time and revest in the Board the
administration of the Plan.

3. SHARES SUBJECT TO THE PLAN.

      (a) Subject to the provisions of paragraph 12 relating to adjustments
upon changes in stock, the shares of the Company's common stock (the "Common
Stock") that may be sold pursuant to rights granted under the Plan shall not
exceed in the aggregate Six Hundred Thousand (600,000) shares Common Stock
(the "Reserved Shares"). As of each January 1, beginning with January 1, 2001
and continuing through and including January 1, 2010 (the "Anniversary
Date"), the number of Reserved Shares will be increased automatically by the
least of (i) 1.5% of the total number of shares of Common Stock outstanding
on such Anniversary Date, (ii) Six Hundred Thousand (600,000) shares, or
(iii) such fewer number of shares as determined by the Board prior to such
Anniversary Date. If any right granted under the Plan shall for any reason
terminate without having been exercised, the shares of Common Stock not
purchased under such right shall again become available for the Plan.

      (b) The stock subject to the Plan may be unissued shares or reacquired
shares, bought on the market or otherwise.

4. GRANT OF RIGHTS; OFFERING.

      (a) The Board or the Committee may from time to time grant or provide for
the grant of rights to purchase Common Stock under the Plan to eligible
employees (an "Offering") on a date or dates (the "Offering Date(s)") selected
by the Board or the Committee. Each Offering shall be in such form and shall
contain such terms and conditions as the Board or the Committee shall deem
appropriate, which shall comply with the requirements of Section 423(b)(5) of
the Code that all employees granted rights to purchase stock under the Plan
shall have the same rights and privileges. The terms and conditions of an
Offering shall be incorporated by reference into the Plan and treated as part of
the Plan. The provisions of separate Offerings need not be identical, but each
Offering shall include (through incorporation of the provisions of this Plan by
reference in the document comprising the Offering or otherwise) the period
during which the Offering shall be effective, which period shall not exceed
twenty-seven (27) months beginning

                                       2.
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with the Offering Date, and the substance of the provisions contained in
paragraphs 5 through 8, inclusive.

      (b) If an employee has more than one right outstanding under the Plan,
unless he or she otherwise indicates in agreements or notices delivered
hereunder: (1) each agreement or notice delivered by that employee will be
deemed to apply to all of his or her rights under the Plan, and (2) a right with
a lower exercise price (or an earlier-granted right, if two rights have
identical exercise prices), will be exercised to the fullest possible extent
before a right with a higher exercise price (or a later-granted right, if two
rights have identical exercise prices) will be exercised.

5. ELIGIBILITY.

      (a) Rights may be granted only to employees of the Company or, as the
Board or the Committee may designate as provided in subparagraph 2(b), to
employees of any Affiliate of the Company. Except as provided in subparagraph
5(b), an employee of the Company or any Affiliate shall not be eligible to be
granted rights under the Plan unless, on the Offering Date, such employee has
been in the employ of the Company or any Affiliate for such continuous period
preceding such grant as the Board or the Committee may require, but in no event
shall the required period of continuous employment be greater than two (2)
years. In addition, unless otherwise determined by the Board or the Committee
and set forth in the terms of the applicable Offering, no employee of the
Company or any Affiliate shall be eligible to be granted rights under the Plan
unless, on the Offering Date, such employee's customary employment with the
Company or such Affiliate is for more than twenty (20) hours per week and more
than five (5) months per calendar year.

      (b) The Board or the Committee may provide that each person who, during
the course of an Offering, first becomes an eligible employee of the Company or
designated Affiliate will, on a date or dates specified in the Offering which
coincides with the day on which such person becomes an eligible employee or
occurs thereafter, receive a right under that Offering, which right shall
thereafter be deemed to be a part of that Offering. Such right shall have the
same characteristics as any rights originally granted under that Offering, as
described herein, except that:

            (i) the date on which such right is granted shall be the "Offering
Date" of such right for all purposes, including determination of the exercise
price of such right;

            (ii) the period of the Offering with respect to such right shall
begin on its Offering Date and end coincident with the end of such Offering; and

            (iii) the Board or the Committee may provide that if such person
first becomes an eligible employee within a specified period of time before the
end of the Offering, he or she will not receive any right under that Offering.

      (c) No employee shall be eligible for the grant of any rights under the
Plan if, immediately after any such rights are granted, such employee would own
stock possessing five percent (5%) or more of the total combined voting power or
value of all classes of stock of the Company or of any Affiliate. For purposes
of this subparagraph 5(c), the rules of Section 424(d)

                                       3.
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of the Code shall apply in determining the stock ownership of any employee, and
stock which such employee may purchase under all outstanding rights and options
shall be treated as stock owned by such employee.

      (d) An eligible employee may be granted rights under the Plan only if such
rights, together with any other rights granted under "employee stock purchase
plans" of the Company and any Affiliates, as specified by Section 423(b)(8) of
the Code, do not permit such employee's rights to purchase stock of the Company
or any Affiliate to accrue at a rate which exceeds twenty-five thousand dollars
($25,000) of fair market value of such stock (determined at the time such rights
are granted) for each calendar year in which such rights are outstanding at any
time.

      (e) Officers of the Company and any designated Affiliate shall be eligible
to participate in Offerings under the Plan, provided, however, that the Board or
the Committee may provide in an Offering that certain employees who are highly
compensated employees within the meaning of Section 423(b)(4)(D) of the Code
shall not be eligible to participate.

6. RIGHTS; PURCHASE PRICE.

      (a) On each Offering Date, each eligible employee, pursuant to an Offering
made under the Plan, shall be granted the right to purchase up to the number of
shares of Common Stock purchasable with a percentage designated by the Board or
the Committee not exceeding twenty percent (20%) of such employee's Earnings (as
defined by the Board for each Offering) during the period which begins on the
Offering Date (or such later date as the Board or the Committee determines for a
particular Offering) and ends on the date stated in the Offering, which date
shall be no later than the end of the Offering. The Board or the Committee shall
establish one or more dates during an Offering (each of which is hereinafter
referred to as a "Purchase Date") on which rights granted under the Plan shall
be exercised and purchases of Common Stock carried out in accordance with such
Offering.

      (b) In connection with each Offering made under the Plan, the Board or the
Committee may specify a maximum number of shares that may be purchased by any
employee as well as a maximum aggregate number of shares that may be purchased
by all eligible employees pursuant to such Offering. In addition, in connection
with each Offering that contains more than one Purchase Date, the Board or the
Committee may specify a maximum aggregate number of shares which may be
purchased by all eligible employees on any given Purchase Date under the
Offering. If the aggregate purchase of shares upon exercise of rights granted
under the Offering would exceed any such maximum aggregate number, the Board or
the Committee shall make a pro rata allocation of the shares available in as
nearly a uniform manner as shall be practicable and as it shall deem to be
equitable.

      (c) The purchase price of stock acquired pursuant to rights granted under
the Plan shall be not less than the lesser of:

            (i) an amount equal to eighty-five percent (85%) of the fair market
value of the stock on the Offering Date; or

            (ii) an amount equal to eighty-five percent (85%) of the fair market
value of the stock on the Purchase Date.

                                       4.
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7. PARTICIPATION; WITHDRAWAL; TERMINATION.

      (a) An eligible employee may become a participant in the Plan pursuant to
an Offering by delivering a participation agreement to the Company within the
time specified in the Offering, in such form as the Company provides. Each such
agreement shall authorize payroll deductions of up to the maximum percentage
specified by the Board or the Committee of such employee's Earnings (as defined
by the Board for each Offering) during the Offering. The payroll deductions made
for each participant shall be credited to an account for such participant under
the Plan and shall be deposited with the general funds of the Company. A
participant may reduce (including to zero) or increase such payroll deductions,
and an eligible employee may begin such payroll deductions, after the beginning
of any Offering only as provided for in the Offering. A participant may make
additional payments into his or her account only if specifically provided for in
the Offering and only if the participant has not had the maximum amount withheld
during the Offering.

      (b) At any time during an Offering, a participant may terminate his or her
payroll deductions under the Plan and withdraw from the Offering by delivering
to the Company a notice of withdrawal in such form as the Company provides. Such
withdrawal may be elected at any time prior to the end of the Offering except as
provided by the Board or the Committee in the Offering. Upon such withdrawal
from the Offering by a participant, the Company shall distribute to such
participant all of his or her accumulated payroll deductions (reduced to the
extent, if any, such deductions have been used to acquire stock for the
participant) under the Offering, without interest, and such participant's right
to acquire Common Stock under that Offering shall be automatically terminated. A
participant's withdrawal from an Offering will have no effect upon such
participant's eligibility to participate in any other Offerings under the Plan
but such participant will be required to deliver a new participation agreement
in order to participate in subsequent Offerings under the Plan.

      (c) Rights granted pursuant to any Offering under the Plan shall terminate
immediately upon cessation of a participant's employment with the Company and
any designated Affiliate, for any reason, and the Company shall distribute to
such terminated employee all of his or her accumulated payroll deductions
(reduced to the extent, if any, such deductions have been used to acquire stock
for the terminated employee), under the Offering, without interest.

      (d) Rights granted under the Plan shall not be transferable by a
participant other than by will or the laws of descent and distribution, or by a
beneficiary designation as provided in paragraph 14, and during a participant's
lifetime, shall be exercisable only by such participant.

8. EXERCISE.

      (a) On each Purchase Date specified in the relevant Offering, each
participant's accumulated payroll deductions and any other additional payments
specifically provided for in the Offering (without any increase for interest)
will be applied to the purchase of whole shares of stock of the Company, up to
the maximum number of shares permitted pursuant to the terms of

                                       5.
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the Plan and the applicable Offering, at the purchase price specified in the
Offering. Unless otherwise provided for in the applicable Offering, no
fractional shares shall be issued upon the exercise of rights granted under the
Plan. The amount, if any, of accumulated payroll deductions remaining in each
participant's account after the purchase of shares which is less than the amount
required to purchase one share of stock on the final Purchase Date of an
Offering shall be held in each such participant's account for the purchase of
shares under the next Offering under the Plan, unless such participant withdraws
from such next Offering, as provided in subparagraph 7(b), or is no longer
eligible to be granted rights under the Plan, as provided in paragraph 5, in
which case such amount shall be distributed to the participant after such final
Purchase Date, without interest. The amount, if any, of accumulated payroll
deductions remaining in any participant's account after the purchase of shares
which is equal to the amount required to purchase whole shares of Common Stock
on the final Purchase Date of an Offering shall be distributed in full to the
participant after such Purchase Date, without interest.

      (b) No rights granted under the Plan may be exercised to any extent unless
the shares to be issued upon such exercise under the Plan (including rights
granted thereunder) are covered by an effective registration statement pursuant
to the Securities Act of 1933, as amended (the "Securities Act") and the Plan is
in material compliance with all applicable state, foreign and other securities
and other laws applicable to the Plan. If on a Purchase Date in any Offering
hereunder the Plan is not so registered or in such compliance, no rights granted
under the Plan or any Offering shall be exercised on such Purchase Date, and the
Purchase Date shall be delayed until the Plan is subject to such an effective
registration statement and such compliance, except that the Purchase Date shall
not be delayed more than twelve (12) months and the Purchase Date shall in no
event be more than twenty-seven (27) months from the Offering Date. If on the
Purchase Date of any Offering hereunder, as delayed to the maximum extent
permissible, the Plan is not registered and in such compliance, no rights
granted under the Plan or any Offering shall be exercised then all payroll
deductions accumulated during the Offering (reduced to the extent, if any, such
deductions have been used to acquire stock) shall be distributed to the
participants, without interest.

9. COVENANTS OF THE COMPANY.

      (a) During the terms of the rights granted under the Plan, the Company
shall at all times make reasonable efforts to keep available the number of
shares of stock required to satisfy such rights, provided that this section
shall not require the Company to take any action that would result in adverse
tax, accounting or financial consequences to the Company.

      (b) The Company shall seek to obtain from each federal, state, foreign or
other regulatory commission or agency having jurisdiction over the Plan such
authority as may be required to issue and sell shares of stock upon exercise of
the rights granted under the Plan. If, after reasonable efforts, the Company is
unable to obtain from any such regulatory commission or agency the authority
which counsel for the Company deems necessary for the lawful issuance and sale
of stock under the Plan, the Company shall be relieved from any liability for
failure to issue and sell stock upon exercise of such rights unless and until
such authority is obtained.

                                       6.
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10. USE OF PROCEEDS FROM STOCK.

      Proceeds from the sale of stock to participants pursuant to rights granted
under the Plan shall constitute general funds of the Company.

11. RIGHTS AS A STOCKHOLDER.

      A participant shall not be deemed to be the holder of, or to have any of
the rights of a holder with respect to, any shares subject to rights granted
under the Plan unless and until the participant's shares acquired upon exercise
of rights hereunder are recorded in the books of the Company (or its transfer
agent).

12. ADJUSTMENTS UPON CHANGES IN STOCK.

      (a) If any change is made in the stock subject to the Plan, or subject to
any rights granted under the Plan (through merger, consolidation,
reorganization, recapitalization, stock dividend, dividend in property other
than cash, stock split, liquidating dividend, combination of shares, exchange of
shares, change in corporate structure or other transaction not involving the
receipt of consideration by the Company), the Plan and outstanding rights will
be appropriately adjusted in the class(es) and maximum number of shares subject
to the Plan and the class(es) and number of shares and price per share of stock
subject to outstanding rights. Such adjustments shall be made by the Board or
the Committee, the determination of which shall be final, binding and
conclusive. (The conversion of any convertible securities of the Company shall
not be treated as a "transaction not involving the receipt of consideration by
the Company.")

      (b) In the event of: (1) a dissolution or liquidation of the Company; (2)
a merger or consolidation in which the Company is not the surviving corporation;
or (3) a reverse merger in which the Company is the surviving corporation but
the shares of Common Stock outstanding immediately preceding the merger are
converted by virtue of the merger into other property, whether in the form of
securities, cash or otherwise, then, as determined by the Board in its sole
discretion, (i) any surviving or acquiring corporation may assume outstanding
rights or substitute similar rights for those under the Plan, (ii) such rights
may continue in full force and effect, or (iii) participants' accumulated
payroll deductions may be used to purchase Common Stock immediately prior to the
transaction described above and the participants' rights under the ongoing
Offering terminated.

13. AMENDMENT OF THE PLAN.

      (a) The Board or the Committee at any time, and from time to time, may
amend the Plan. However, except as provided in paragraph 12 relating to
adjustments upon changes in stock, no amendment shall be effective unless
approved by the stockholders of the Company within twelve (12) months before or
after the adoption of the amendment if such amendment requires stockholder
approval in order for the Plan to obtain employee stock purchase plan treatment
under Section 423 of the Code or to comply with the requirements of Rule 16b-3
promulgated under the Exchange Act.

      (b) The Board or the Committee may amend the Plan in any respect the Board
or the Committee deems necessary or advisable to provide eligible employees with
the maximum

                                       7.
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benefits provided or to be provided under the provisions of the Code and the
regulations promulgated thereunder relating to employee stock purchase plans
and/or to bring the Plan and/or rights granted under it into compliance
therewith.

      (c) Rights and obligations under any rights granted before amendment of
the Plan shall not be impaired by any amendment of the Plan, except with the
consent of the person to whom such rights were granted, or except as necessary
to comply with any laws or governmental regulations, or except as necessary to
ensure that the Plan and/or rights granted under the Plan comply with the
requirements of Section 423 of the Code.

14. DESIGNATION OF BENEFICIARY.

      (a) A participant may file a written designation of a beneficiary who is
to receive any shares and cash, if any, from the participant's account under the
Plan in the event of such participant's death subsequent to the end of an
Offering but prior to delivery to the participant of such shares and cash. In
addition, a participant may file a written designation of a beneficiary who is
to receive any cash from the participant's account under the Plan in the event
of such participant's death during an Offering.

      (b) Such designation of beneficiary may be changed by the participant at
any time by written notice in the form prescribed by the Company. In the event
of the death of a participant and in the absence of a beneficiary validly
designated under the Plan who is living at the time of such participant's death,
the Company shall deliver such shares and/or cash to the executor or
administrator of the estate of the participant, or if no such executor or
administrator has been appointed (to the knowledge of the Company), the Company,
in its sole discretion, may deliver such shares and/or cash to the spouse or to
any one or more dependents or relatives of the participant, or if no spouse,
dependent or relative is known to the Company, then to such other person as the
Company may designate.

15. TERMINATION OR SUSPENSION OF THE PLAN.

      (a) The Board or the Committee in its discretion, may suspend or terminate
the Plan at any time. No rights may be granted under the Plan while the Plan is
suspended or after it is terminated.

      (b) Rights and obligations under any rights granted while the Plan is in
effect shall not be impaired by suspension or termination of the Plan, except as
expressly provided in the Plan or with the consent of the person to whom such
rights were granted, or except as necessary to comply with any laws or
governmental regulation, or except as necessary to ensure that the Plan and/or
rights granted under the Plan comply with the requirements of Section 423 of the
Code.

                                       8.
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16. EFFECTIVE DATE OF PLAN.

      The Plan shall become effective upon the effective date of the initial
public offering of Common Stock (the "Effective Date"), but no rights granted
under the Plan shall be exercised unless and until the Plan has been approved by
the stockholders of the Company within twelve (12) months before or after the
date the Plan is adopted by the Board, which date may be prior to the Effective
Date.

                                       9.

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