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                                                                    EXHIBIT 4.12

                                 VIROLOGIC, INC.

                           2000 EQUITY INCENTIVE PLAN

                           ADOPTED FEBRUARY 21, 2000
                 APPROVED BY STOCKHOLDERS _______________, 2000
                     TERMINATION DATE: _______________, 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.

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

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

        (e) "COMMON STOCK" means the common stock of the Company.

        (f) "COMPANY" means VIROLOGIC, INC., a Delaware corporation.

        (g) "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

                                       1.

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for their services as Directors or Directors who are merely paid a director's
fee by the Company for their services as Directors.

        (h) "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 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. For purposes of Incentive Stock Options, no such leave
may exceed 90 days, unless reemployment upon expiration of such leave is
guaranteed by statute or contract, including Company policies. If reemployment
upon expiration of a leave of absence approved by the Company is not so
guaranteed, on the 91st day of such leave any Incentive Stock Option held by an
Optionholder shall be treated for tax purposes as a Nonstatutory Stock Option.

        (i) "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.

        (j) "DIRECTOR" means a member of the Board of Directors of the Company.

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

        (l) "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.

        (m) "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.

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

                                       2.

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

        (o) "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.

        (p) "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 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.

        (q) "NONSTATUTORY STOCK OPTION" means an Option not intended to qualify
as an Incentive Stock Option.

        (r) "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.

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

        (t) "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.

        (u) "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.

        (v) "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.

        (w) "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.

        (x) "PLAN" means this VIROLOGIC, INC. 2000 Equity Incentive Plan.

                                       3.

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        (y) "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.

        (z) "SECURITIES ACT" means the Securities Act of 1933, as amended.

        (aa) "STOCK AWARD" means any right granted under the Plan, including an
Option, a stock bonus and a right to acquire restricted stock.

        (bb) "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.

        (cc) "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
12.

               (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

                                       4.

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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 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 11 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 two
hundred thousand (4,200,000) shares of Common Stock (post-split).

        (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 and Consultants.

        (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

                                       5.

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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 11
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 forth in the
preceding sentence if such Option is granted pursuant to an assumption or

                                       6.

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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.

        In the case of any deferred payment arrangement, 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 amounts other than amounts stated to be interest
under the deferred payment arrangement.

        (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.

                                       7.

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        (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 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 twelve (12) 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

                                       8.

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Agreement. If, after death, the Option is not exercised within the time
specified herein, the Option shall terminate.

        (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. The Company will not exercise its repurchase
option until at least six (6) months (or such longer or shorter period of time
required to avoid a charge to earnings for financial accounting purposes) have
elapsed following exercise of the Option unless the Board otherwise specifically
provides in the Option.

        (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 9(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.      PROVISIONS OF STOCK AWARDS OTHER THAN OPTIONS.

                                       9.

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        (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 repurchase option 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.

        (b) RESTRICTED STOCK 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.

                                      10.

<PAGE>   11
               (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.

8.      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 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.

9.      USE OF PROCEEDS FROM STOCK.

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

10.     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

                                      11.

<PAGE>   12
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 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

                                      12.

<PAGE>   13
Common Stock under the Stock Award, provided, however, that no shares of Common
Stock are withheld with a value exceeding the minimum amount of tax required to
be withheld by law; or (iii) delivering to the Company owned and unencumbered
shares of Common Stock.

11.     ADJUSTMENTS UPON CHANGES IN 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) CHANGE IN CONTROL--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) CHANGE IN CONTROL--ASSET SALE, MERGER, CONSOLIDATION OR REVERSE
MERGER. In the event of (i) a sale, lease or other disposition of all or
substantially all of the assets of the Company, (ii) a merger or consolidation
in which the Company is not the surviving corporation or (iii) 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 any surviving corporation or acquiring corporation shall assume
any Stock Awards outstanding under the Plan or shall substitute similar stock
awards (including an award to acquire the same consideration paid to the
stockholders in the transaction described in this subsection 11(c) for those
outstanding under the Plan). 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, 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 event. With
respect to any other Stock Awards outstanding under the Plan, such Stock Awards
shall terminate if not exercised (if applicable) prior to such event.

12.     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 11 relating to
adjustments upon changes in Common Stock, no amendment shall be effective unless
approved by the stockholders of the

                                      13.

<PAGE>   14
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.

13.     TERMINATION OR SUSPENSION OF THE PLAN.

        (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.

14.     EFFECTIVE DATE OF PLAN.

        The Plan shall become effective as determined by the Board, 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.

15.     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.

                                      14.<PAGE>   1
                                                                    EXHIBIT 4.13

                                VIROLOGIC, INC.

                                 1996 STOCK PLAN

                             STOCK OPTION AGREEMENT
--------------------------------------------------------------------------------

        Unless otherwise defined herein, the terms defined in the Plan shall
have the same defined meanings in this Option Agreement.

I.      NOTICE OF STOCK OPTION GRANT

[Name]
[Address]

        You have been granted an option to purchase Common Stock of the Company,
subject to the terms and conditions of the Plan and this Option Agreement, as
follows:

        Date of Grant

        Vesting Commencement Date

        Exercise Price per Share

        Total Number of Shares Granted

        Total Exercise Price

        Type of Option:                          ___Incentive Stock Option

                                                 ___Nonstatutory Stock Option

        Term/Expiration Date:

                                       1.
<PAGE>   2
        VESTING SCHEDULE:

        This Option may be exercised, in whole or in part, in accordance with
the following schedule:

         [Vesting Schdule]

        TERMINATION PERIOD:

         This Option may be exercised for 30 days after termination of
employment or consulting relationship, or such longer period as may be
applicable upon death or disability of Optionee as provided in the Plan, but in
no event later than the Term/Expiration Date as provided above.

II.     AGREEMENT

               1. GRANT OF OPTION. ViroLogic, Inc., a Delaware corporation (the
"Company"), hereby grants to the Optionee named in the Notice of Grant (the
"Optionee"), an option (the "Option") to purchase the total number of shares of
Common Stock (the "Shares") set forth in the Notice of Grant, at the exercise
price per share set forth in the Notice of Grant (the "Exercise Price") subject
to the terms, definitions and provisions of the 1996 Stock Plan (the "Plan")
adopted by the Company, which is incorporated herein by reference. Unless
otherwise defined herein, the terms defined in the Plan shall have the same
defined meanings in this Option.

              If designated in the Notice of Grant as an Incentive Stock Option
("ISO"), this Option is intended to qualify as an Incentive Stock Option as
defined in Section 422 of the Code. However, if this Option is intended to be an
Incentive Stock Option, to the extent that it exceeds the $100,000 rule of Code
Section 422(d) it shall be treated as a Nonstatutory Stock Option ("NSO").

               2. EXERCISE OF OPTION. This Option shall be exercisable during
its term in accordance with the Vesting Schedule set out in the Notice of Grant
and with the provisions of Section 9 of the Plan as follows:

                      a.     RIGHT TO EXERCISE.

                             (i) This Option may not be exercised for a fraction
of a Share.

                             (ii) In the event of Optionee's death, disability
or other termination of the employment or consulting relationship, the
exercisability of the Option is governed by Sections 5, 6 and 7 below, subject
to the limitation contained in subsection 2(a)(iii).

                             (iii) In no event may this Option be exercised
after the date of expiration of the term of this Option as set forth in the
Notice of Grant.

                      b. METHOD OF EXERCISE. This Option shall be exercisable by
written notice (in the form attached as Exhibit A) which shall state the
election to exercise the Option, the number of Shares in respect of which option
is being exercised, and such other

                                       2.
<PAGE>   3
representations and agreements as to the holder's investment intent with respect
to such shares of Common Stock as may be required by the Company pursuant to the
provisions of the Plan. Such written notice shall be signed by the Optionee and
shall be delivered in person or by certified mail to the Secretary of the
Company. The written notice shall be accompanied by payment of the Exercise
Price. This Option shall be deemed to be exercised upon receipt by the Company
of such written notice accompanied by the Exercise Price.

              No Shares will be issued pursuant to the exercise of an Option
unless such issuance and such exercise shall comply with all relevant provisions
of law and the requirements of any stock exchange upon which the Shares may then
be listed. Assuming such compliance, for income tax purposes the Shares shall be
considered transferred to the Optionee on the date on which the Option is
exercised with respect to such Shares.

               3. OPTIONEE'S REPRESENTATIONS. In the event the Shares
purchasable pursuant to the exercise of this Option have not been registered
under the Securities Act of 1933, as amended, at the time this Option is
exercised, Optionee shall, if required by the Company, concurrently with the
exercise of all or any portion of this Option, deliver to the Company his or her
Investment Representation Statement in the form attached hereto as Exhibit B,
and shall read the applicable rules of the Commissioner of Corporations attached
to such Investment Representation Statement.

               4. METHOD OF PAYMENT. Payment of the Exercise Price shall be by
any of the following, or a combination thereof, at the election of the Optionee:

                      a. cash; or

                      b. check; or

                      c. surrender of other shares of Common Stock of the
Company which (A) in the case of Shares acquired pursuant to the exercise of a
Company option, have been owned by the Optionee for more than six (6) months on
the date of surrender, and (B) have a Fair Market Value on the date of surrender
equal to the Exercise Price of the Shares as to which the Option is being
exercised; or

                      d. delivery of a properly executed exercise notice
together with such other documentation as the Administrator and the broker, if
applicable, shall require to effect an exercise of the Option and delivery to
the Company of the sale or loan proceeds required to pay the Exercise Price.

               5. TERMINATION OF RELATIONSHIP. In the event an Optionee's
Continuous Status as an Employee or Consultant terminates, Optionee may, to the
extent otherwise so entitled at the date of such termination (the "Termination
Date"), exercise this Option during the Termination Period set out in the Notice
of Grant. To the extent that Optionee was not entitled to exercise this Option
at the date of such termination, or if Optionee does not exercise this Option
within the time specified herein, the Option shall terminate.

               6. DISABILITY OF OPTIONEE. Notwithstanding the provisions of
Section 5 above, in the event of termination of an Optionee's consulting
relationship or Continuous Status

                                       3.
<PAGE>   4
as an Employee as a result of his or her disability, Optionee may, but only
within six (6) months from the date of such termination (and in no event later
than the expiration date of the term of such Option as set forth in the Option
Agreement), exercise the Option to the extent otherwise entitled to exercise it
at the date of such termination; provided, however, that if such disability is
not a "disability" as such term is defined in Section 22(e)(3) of the Code, in
the case of an Incentive Stock Option such Incentive Stock Option shall
automatically convert to a Nonstatutory Stock Option on the day three months and
one day following such termination. To the extent that Optionee was not entitled
to exercise the Option at the date of termination, or if Optionee does not
exercise such Option to the extent so entitled within the time specified herein,
the Option shall terminate, and the Shares covered by such Option shall revert
to the Plan.

               7. DEATH OF OPTIONEE. In the event of termination of Optionee's
Continuous Status as an Employee or Consultant as a result of the death of
Optionee, the Option may be exercised at any time within twelve (12) months
following the date of death (but in no event later than the date of expiration
of the term of this Option as set forth in Section 9 below), by Optionee's
estate or by a person who acquired the right to exercise the Option by bequest
or inheritance, but only to the extent the Optionee could exercise the Option at
the date of death.

               8. NON-TRANSFERABILITY OF OPTION. This Option may not be
transferred in any manner otherwise than by will or by the laws of descent or
distribution and may be exercised during the lifetime of Optionee only by
Optionee. The terms of this Option shall be binding upon the executors,
administrators, heirs, successors and assigns of the Optionee.

               9. TERM OF OPTION. This Option may be exercised only within the
term set out in the Notice of Grant, and may be exercised during such term only
in accordance with the Plan and the terms of this Option. The limitations set
out in Section 7 of the Plan regarding Options designated as Incentive Stock
Options and Options granted to more than ten percent (10%) shareholders shall
apply to this Option.

               10. TAXATION UPON EXERCISE OF OPTION. Optionee understands that,
upon exercising a Nonstatutory Option, he or she will recognize income for tax
purposes in an amount equal to the excess of the then Fair Market Value of the
Shares over the exercise price. However, the timing of this income recognition
may be deferred for up to six months if Optionee is subject to Section 16 of the
Securities Exchange Act of 1934, as amended (the "Exchange Act"). If the
Optionee is an Employee, the Company will be required to withhold from
Optionee's compensation, or collect from Optionee and pay to the applicable
taxing authorities an amount equal to a percentage of this compensation income.
Additionally, the Optionee may at some point be required to satisfy tax
withholding obligations with respect to the disqualifying disposition of an
Incentive Stock Option. The Optionee shall satisfy his or her tax withholding
obligation arising upon the exercise of this Option out of Optionee's
compensation or by payment to the Company.

               11. TAX CONSEQUENCES. Set forth below is a brief summary as of
the date of this Option of some of the federal and California tax consequences
of exercise of this Option and disposition of the Shares. THIS SUMMARY IS
NECESSARILY INCOMPLETE, AND THE TAX LAWS AND REGULATIONS ARE SUBJECT TO CHANGE.
OPTIONEE SHOULD

                                       4.
<PAGE>   5
CONSULT A TAX ADVISER BEFORE EXERCISING THIS OPTION OR DISPOSING OF THE SHARES.

                      a. EXERCISE OF ISO. If this Option qualifies as an ISO,
there will be no regular federal income tax liability or California income tax
liability upon the exercise of the Option, although the excess, if any, of the
Fair Market Value of the Shares on the date of exercise over the Exercise Price
will be treated as an adjustment to the alternative minimum tax for federal tax
purposes and may subject the Optionee to the alternative minimum tax in the year
of exercise.

                      b. EXERCISE OF ISO FOLLOWING DISABILITY. If the Optionee's
Continuous Status as an Employee or Consultant terminates as a result of
disability that is not total and permanent disability as defined in Section
22(e)(3) of the Code, to the extent permitted on the date of termination, the
Optionee must exercise an ISO within 90 days of such termination for the ISO to
be qualified as an ISO.

                      c. EXERCISE OF NONSTATUTORY STOCK OPTION. There may be a
regular federal income tax liability and California income tax liability upon
the exercise of a Nonstatutory Stock Option. The Optionee will be treated as
having received compensation income (taxable at ordinary income tax rates) equal
to the excess, if any, of the Fair Market Value of the Shares on the date of
exercise over the Exercise Price. If Optionee is an Employee or a former
Employee, the Company will be required to withhold from Optionee's compensation
or collect from Optionee and pay to the applicable taxing authorities an amount
in cash equal to a percentage of this compensation income at the time of
exercise, and may refuse to honor the exercise and refuse to deliver Shares if
such withholding amounts are not delivered at the time of exercise.

                      d. DISPOSITION OF SHARES. In the case of an NSO, if Shares
are held for at least one year, any gain realized on disposition of the Shares
will be treated as long-term capital gain for federal and California income tax
purposes. In the case of an ISO, if Shares transferred pursuant to the Option
are held for at least one year after exercise and are disposed of at least two
years after the Date of Grant, any gain realized on disposition of the Shares
will also be treated as long-term capital gain for federal and California income
tax purposes. If Shares purchased under an ISO are disposed of within such
one-year period or within two years after the Date of Grant, any gain realized
on such disposition will be treated as compensation income (taxable at ordinary
income rates) to the extent of the difference between the Exercise Price and the
lesser of (1) the Fair Market Value of the Shares on the date of exercise, or
(2) the sale price of the Shares.

                      e. NOTICE OF DISQUALIFYING DISPOSITION OF ISO SHARES. If
the Option granted to Optionee herein is an ISO, and if Optionee sells or
otherwise disposes of any of the Shares acquired pursuant to the ISO on or
before the later of (1) the date two years after the Date of Grant, or (2) the
date one year after the date of exercise, the Optionee shall immediately notify
the Company in writing of such disposition. Optionee agrees that Optionee may be
subject to income tax withholding by the Company on the compensation income
recognized by the Optionee.

                                       5.
<PAGE>   6
               12. ENTIRE AGREEMENTS GOVERNING LAW. The Plan is incorporated
herein by reference. The Plan and this Option Agreement constitute the entire
agreement of the parties with respect to the subject matter hereof and supersede
in their entirety all prior undertakings and agreements of the Company and
Optionee with respect to the subject matter hereof, and may not be modified
adversely to the Optionee's interest except by means of a writing signed by the
Company and Optionee. This agreement is governed by California law except for
that body of law pertaining to conflict of laws.

                                       VIROLOGIC, INC.
                                       a Delaware corporation

                                       By:
                                          --------------------------------------

                                       Its:
                                           -------------------------------------

                                       6.
<PAGE>   7
        OPTIONEE ACKNOWLEDGES AND AGREES THAT THE VESTING OF SHARES PURSUANT TO
THE OPTION HEREOF IS EARNED ONLY BY CONTINUING CONSULTANCY OR EMPLOYMENT AT THE
WILL OF THE COMPANY (NOT THROUGH THE ACT OF BEING HIRED, BEING GRANTED THIS
OPTION OR ACQUIRING SHARES HEREUNDER). OPTIONEE FURTHER ACKNOWLEDGES AND AGREES
THAT NOTHING IN THIS AGREEMENT, NOR IN THE COMPANY'S STOCK OPTION PLAN WHICH IS
INCORPORATED HEREIN BY REFERENCE, SHALL CONFER UPON OPTIONEE ANY RIGHT WITH
RESPECT TO CONTINUATION OF EMPLOYMENT OR CONSULTANCY BY THE COMPANY, NOR SHALL
IT INTERFERE IN ANY WAY WITH OPTIONEE'S RIGHT OR THE COMPANY'S RIGHT TO
TERMINATE OPTIONEE'S EMPLOYMENT OR CONSULTANCY AT ANY TIME, WITH OR WITHOUT
CAUSE.

          Optionee acknowledges receipt of a copy of the Plan and represents
   that he is familiar with the terms and provisions thereof, and hereby accepts
   this Option subject to all of the terms and provisions thereof. Optionee has
   reviewed the Plan and this Option in their entirety, has had an opportunity
   to obtain the advice of counsel prior to executing this Option and fully
   understands all provisions of the Option. Optionee hereby agrees to accept as
   binding, conclusive and final all decisions or interpretations of the
   Administrator upon any questions arising under the Plan or this Option.
   Optionee further agrees to notify the Company upon any change in the
   residence address indicated below.

        Dated:                                 ---------------------------------
               ------------------------        Optionee

                                               Residence Address:

                                               ---------------------------------

                                               ---------------------------------

                                       7.
<PAGE>   8
                                    EXHIBIT A

                                 1996 STOCK PLAN

                                 EXERCISE NOTICE

ViroLogic, Inc.
270 E. Grand Avenue
South San Francisco, CA 94080
Attention: Secretary

               1. EXERCISE OF OPTION. Effective as of today, _______, 20___, the
undersigned ("Optionee") hereby elects to exercise Optionee's option to purchase
________ shares of the Common Stock (the "Shares") of ViroLogic, Inc. (the
"Company") under and pursuant to the 1996 Stock Plan, as amended (the "Plan")
and the [ ] Incentive [X] Nonstatutory Stock Option Agreement dated ________,
20__ (the "Option Agreement").

               2. REPRESENTATIONS OF OPTIONEE. Optionee acknowledges that
Optionee has received, read and understood the Plan and the Option Agreement and
agrees to abide by and be bound by their terms and conditions.

               3. RIGHTS AS SHAREHOLDER. Until the stock certificate evidencing
such Shares is issued (as evidenced by the appropriate entry on the books of the
Company or of a duly authorized transfer agent of the Company), no right to vote
or receive dividends or any other rights as a shareholder shall exist with
respect to the Optioned Stock, notwithstanding the exercise of the Option. The
Company shall issue (or cause to be issued) such stock certificate promptly
after the Option is exercised. No adjustment will be made for a dividend or
other right for which the record date is prior to the date the stock certificate
is issued, except as provided in Section 12 of the Plan.

               Optionee shall enjoy rights as a shareholder until such time as
Optionee disposes of the Shares or the Company and/or its assignee(s) exercises
the Right of First Refusal hereunder. Upon such exercise, Optionee shall have no
further rights as a holder of the Shares so purchased except the right to
receive payment for the Shares so purchased in accordance with the provisions of
this Agreement, and Optionee shall forthwith cause the certificate(s) evidencing
the Shares so purchased to be surrendered to the Company for transfer or
cancellation.

               4. COMPANY'S RIGHT OF FIRST REFUSAL. Before any Shares held by
Optionee or any transferee (either being sometimes referred to herein as the
"Holder") may be sold or otherwise transferred (including transfer by gift or
operation of law), the Company or its assignee(s) shall have a right of first
refusal to purchase the Shares on the terms and conditions set forth in this
Section (the "Right of First Refusal").

                      a. NOTICE OF PROPOSED TRANSFER. The Holder of the Shares
shall deliver to the Company a written notice (the "Notice") stating: (i) the
Holder's bona fide intention to sell or otherwise transfer such Shares; (ii) the
name of each proposed purchaser or other transferee ("Proposed Transferee");
(iii) the number of Shares to be transferred to each Proposed Transferee; and
(iv) the bona fide cash price or other consideration for which the

<PAGE>   9
Holder proposes to transfer the Shares (the "Offered Price"), and the Holder
shall offer the Shares at the Offered Price to the Company or its assignee(s).

                      b. EXERCISE OF RIGHT OF FIRST REFUSAL. At any time within
thirty (30) days after receipt of the Notice, the Company and/or its assignee(s)
may, by giving written notice to the Holder, elect to purchase all, but not less
than all, of the Shares proposed to be transferred to any one or more of the
Proposed Transferees, at the purchase price determined in accordance with
subsection (c) below.

                      c. PURCHASE PRICE. The purchase price ("Purchase Price")
for the Shares purchased by the Company or its assignee(s) under this Section
shall be the Offered Price. If the Offered Price includes consideration other
than cash, the cash equivalent value of the non-cash consideration shall be
determined by the Board of Directors of the Company in good faith.

                      d. PAYMENT. Payment of the Purchase Price shall be made,
at the option of the Company or its assignee(s), in cash (by check), by
cancellation of all or a portion of any outstanding indebtedness of the Holder
to the Company (or, in the case of repurchase by an assignee, to the assignee),
or by any combination thereof within 30 days after receipt of the Notice or in
the manner and at the times set forth in the Notice.

                      e. HOLDER'S RIGHT TO TRANSFER. If all of the Shares
proposed in the Notice to be transferred to a given Proposed Transferee are not
purchased by the Company and/or its assignee(s) as provided in this Section,
then the Holder may sell or otherwise transfer such Shares to that Proposed
Transferee at the Offered Price or at a higher price, provided that such sale or
other transfer is consummated within 120 days after the date of the Notice and
provided further that any such sale or other transfer is effected in accordance
with any applicable securities laws and the Proposed Transferee agrees in
writing that the provisions of this Section shall continue to apply to the
Shares in the hands of such Proposed Transferee. If the Shares described in the
Notice are not transferred to the Proposed Transferee within such period, a new
Notice shall be given to the Company, and the Company and/or its assignees shall
again be offered the Right of First Refusal before any Shares held by the Holder
may be sold or otherwise transferred.

                      f. EXCEPTION FOR CERTAIN FAMILY TRANSFERS. Anything to the
contrary contained in this Section notwithstanding, the transfer of any or all
of the Shares during the Optionee's lifetime or on the Optionee's death by will
or intestacy to the Optionee's immediate family or a trust for the benefit of
the Optionee's immediate family shall be exempt from the provisions of this
Section. "Immediate Family" as used herein shall mean spouse, lineal descendant
or antecedent, father, mother, brother or sister. In such case, the transferee
or other recipient shall receive and hold the Shares so transferred subject to
the provisions of this Section, and there shall be no further transfer of such
Shares except in accordance with the terms of this Section.

                      g. TERMINATION OF RIGHT OF FIRST REFUSAL. The Right of
First Refusal shall terminate as to any Shares 90 days after the first sale of
Common Stock of the Company to the general public pursuant to a registration
statement filed with and declared

                                       2.
<PAGE>   10
effective by the Securities and Exchange Commission under the Securities Act of
1933, as amended.

               5. TAX CONSULTATION. Optionee understands that Optionee may
suffer adverse consequences as a result of Optionee's purchase or disposition of
the Shares. Optionee represents that Optionee has consulted with any tax
consultants Optionee deems advisable in connection with the purchase or
disposition of the Shares and that Optionee is not relying on the Company for
any tax advice.

               6. RESTRICTIVE LEGENDS AND STOP TRANSFER ORDERS.

                      a. LEGENDS. optionee understands and agrees that the
Company shall cause the legends set forth below or legends substantially
equivalent thereto, to be placed upon any certificate(s) evidencing ownership of
the Shares together with any other legends that may be required by the Company
or by state or federal securities laws:

               THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER
               THE SECURITIES ACT OF 1933 (THE "ACT") AND MAY NOT BE OFFERED,
               SOLD OR OTHERWISE TRANSFERRED, PLEDGED OR HYPOTHECATED UNLESS AND
               UNTIL REGISTERED UNDER THE ACT OR, IN THE OPINION OF COUNSEL
               SATISFACTORY TO THE ISSUER OF THESE SECURITIES, SUCH OFFER, SALE
               OR TRANSFER, PLEDGE OR HYPOTHECATION IS IN COMPLIANCE THEREWITH.

               THE SHARES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO CERTAIN
               RESTRICTIONS ON TRANSFER AND A RIGHT OF FIRST REFUSAL HELD BY THE
               ISSUER OR ITS ASSIGNEE(S) AS SET FORTH IN THE EXERCISE NOTICE
               BETWEEN THE ISSUER AND THE ORIGINAL HOLDER OF THESE SHARES, A
               COPY OF WHICH MAY BE OBTAINED AT THE PRINCIPAL OFFICE OF THE
               ISSUER SUCH TRANSFER RESTRICTIONS AND RIGHT OF FIRST REFUSAL ARE
               BINDING ON TRANSFEREES OF THESE SHARES.

               IT IS UNLAWFUL TO CONSUMMATE A SALE OR TRANSFER OF THIS SECURITY,
               OR ANY INTEREST THEREIN, OR TO RECEIVE ANY CONSIDERATION
               THEREFOR, WITHOUT THE PRIOR WRITTEN CONSENT OF THE COMMISSIONER
               OF CORPORATIONS OF THE STATE OF CALIFORNIA, EXCEPT AS PERMITTED
               IN THE COMMISSIONERS RULES.

               Optionee understands that transfer of the Shares may be
restricted by Section 260.141.11 of the Rules of the California Corporations
Commissioner, a copy of which

                                       3.
<PAGE>   11
is attached to Exhibit B, the Investment Representation Statement.

                      b. STOP-TRANSFER NOTICES. Optionee agrees that, in order
to ensure compliance with the restrictions referred to herein, the Company may
issue appropriate "stop transfer" instructions to its transfer agent, if any,
and that, if the Company transfers its own securities, it may make appropriate
notations to the same effect in its own records.

                      c. REFUSAL TO TRANSFER. The Company shall not be required
(i) to transfer on its books any Shares that have been sold or otherwise
transferred in violation of any of the provisions of this Agreement or (ii) to
treat as owner of such Shares or to accord the right to vote or pay dividends to
any purchaser or other transferee to whom such Shares shall have been so
transferred.

               7. SUCCESSORS AND ASSIGNS. The Company may assign any of its
rights under this Agreement to single or multiple assignees, and this Agreement
shall inure to the benefit of the successors and assigns of the Company. Subject
to the restrictions on transfer herein set forth, this Agreement shall be
binding upon Optionee and his or her heirs, executors, administrators,
successors and assigns.

               8. INTERPRETATION. Any dispute regarding the interpretation of
this Agreement shall be submitted by Optionee or by the Company forthwith to the
Company's Board of Directors or the committee thereof that administers the Plan,
which shall review such dispute at its next regular meeting. The resolution of
such a dispute by the Board or committee shall be final and binding on the
Company and on Optionee.

               9. GOVERNING LAW; SEVERABILITY. This Agreement shall be governed
by and construed in accordance with the laws of the State of California
excluding that body of law pertaining to conflicts of law. Should any provision
of this Agreement be determined by a court of law to be illegal or
unenforceable, the other provisions shall nevertheless remain effective and
shall remain enforceable.

               10. NOTICE. Any notice required or permitted hereunder shall be
given in writing and shall be deemed effectively given upon personal delivery or
upon deposit in the United States mail by certified mail, with postage and fees
prepaid, addressed to the other party at its address as shown below beneath its
signature, or to such other address as such party may designate in writing from
time to time to the other party.

               11. FURTHER INSTRUMENTS. The parties agree to execute such
further instruments and to take such further action as may be reasonably
necessary to carry out the purposes and intent of this Agreement.

               12. DELIVERY OF PAYMENT. Optionee herewith delivers to the
Company the full Exercise Price for the Shares.

               13. ENTIRE AGREEMENT. The Plan and Notice of Grant/Option
Agreement are incorporated herein by reference. This Agreement, the Plan, the
Option Agreement and the Investment Representation Statement constitute the
entire agreement of the parties with respect to the subject matter hereof and
supersede in their entirety all prior undertakings and agreements

                                       4.
<PAGE>   12
of the Company and Purchaser with respect to the subject matter hereof, and may
not be modified adversely to the Purchaser's interest except by means of a
writing signed by the Company and Purchaser.

Submitted by:                               Accepted by:

OPTIONEE:                                   VIROLOGIC, INC.

                                            By:
                                               ---------------------------------
                                            Its:
                                                --------------------------------

-------------------------------
(Signature)

Address:                                    Address:

--------------------------------            ------------------------------------

--------------------------------            ------------------------------------

                                       5.
<PAGE>   13
                      (TO BE COMPLETED AT TIME OF EXERCISE)

                                    EXHIBIT B

                       INVESTMENT REPRESENTATION STATEMENT

OPTIONEE:

Company:                     VIROLOGIC, INC.

SECURITY:                    COMMON STOCK

AMOUNT:

DATE:

In connection with the purchase of the above-listed Securities, the undersigned
Optionee represents to the Company the following:

                      a. Optionee is aware of the Company's business affairs and
financial condition and has acquired sufficient information about the Company to
reach an informed and knowledgeable decision to acquire the Securities. Optionee
is acquiring these Securities for investment for Optionee's own account only and
not with a view to, or for resale in connection with, any "distribution" thereof
within the meaning of the Securities Act of 1933, as amended (the "Securities
Act").

                      b. Optionee acknowledges and understands that the
Securities constitute "restricted securities" under the Securities Act and have
not been registered under the Securities Act in reliance upon a specific
exemption therefrom, which exemption depends upon, among other things, the bona
fide nature of Optionee's investment intent as expressed herein. In this
connection, Optionee understands that, in the view of the Securities and
Exchange Commission, the statutory basis for such exemption may be unavailable
if Optionee's representation was predicated solely upon a present intention to
hold these Securities for the minimum capital gains period specified under tax
statutes, for a deferred sale, for or until an increase or decrease in the
market price of the Securities, or for a period of one year or any other fixed
period in the future. Optionee further understands that the Securities must be
held indefinitely unless they are subsequently registered under the Securities
Act or an exemption from such registration is available. Optionee further
acknowledges and understands that the Company is under no obligation to register
the Securities. Optionee understands that the certificate evidencing the
Securities will be imprinted with a legend which prohibits the transfer of the
Securities unless they are registered or such registration is not required in
the opinion of counsel satisfactory to the Company, a legend prohibiting their
transfer without the consent of the Commissioner of Corporations of the State of
California and any other legend required under applicable state securities laws.

                      c. Optionee is familiar with the provisions of Rule 701
and Rule 144, each promulgated under the Securities Act, which, in substance,
permit limited public resale of "restricted securities" acquired, directly or
indirectly from the issuer thereof, in a nonpublic

<PAGE>   14
offering subject to the satisfaction of certain conditions. Rule 701 provides
that if the issuer qualifies under Rule 701 at the time of the grant of the
Option to the Optionee, the exercise will be exempt from registration under the
Securities Act. In the event the Company becomes subject to the reporting
requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934,
ninety (90) days thereafter (or such longer period as any market stand-off
agreement may require) the Securities exempt under Rule 701 may be resold,
subject to the satisfaction of certain of the conditions specified by Rule 144,
including: (1) the resale being made through a broker in an unsolicited
"broker's transaction" or in transactions directly with a market maker (as said
term is defined under the Securities Exchange Act of 1934); and, in the case of
an affiliate, (2) the availability of certain public information about the
Company, (3) the amount of Securities being sold during any three month period
not exceeding the limitations specified in Rule 144(e), and (4) the timely
filing of a Form 144, if applicable.

               In the event that the Company does not qualify under Rule 701 at
the time of grant of the Option, then the Securities may be resold in certain
limited circumstances subject to the provisions of Rule 144, which requires the
resale to occur not less than two years after the later of the date the
Securities were sold by the Company or the date the Securities were sold by an
affiliate of the Company, within the meaning of Rule 144; and, in the case of
acquisition of the Securities by an affiliate, or by a non-affiliate who
subsequently holds the Securities less than three years, the satisfaction of the
conditions set forth in sections (1), (2), (3) and (4) of the paragraph
immediately above.

                      d. Optionee hereby agrees that if so requested by the
Company or any representative of the underwriters in connection with any
registration of the offering of any securities of the Company under the
Securities Act, Optionee shall not sell or otherwise transfer any Shares or
other securities of the Company during the 180-day period following the
effective date of a registration statement of the Company filed under the
Securities Act; provided, however, that such restriction shall only apply to the
first registration statement of the Company to become effective under the
Securities Act which include securities to be sold on behalf of the Company to
the public in an underwritten public offering under the Securities Act. The
Company may impose stop-transfer instructions with respect to securities subject
to the foregoing restrictions until the end of such 180-day period.

                      e. Optionee further understands that in the event all of
the applicable requirements of Rule 701 or 144 are not satisfied, registration
under the Securities Act, compliance with Regulation A, or some other
registration exemption will be required; and that, notwithstanding the fact that
Rules 144 and 701 are not exclusive, the Staff of the Securities and Exchange
Commission has expressed its opinion that persons proposing to sell private
placement securities other than in a registered offering and otherwise than
pursuant to Rules 144 or 701 will have a substantial burden of proof in
establishing that an exemption from registration is available for such offers or
sales, and that such persons and their respective brokers who participate in
such transactions do so at their own risk. Optionee understands that no
assurances can be given that any such other registration exemption will be
available in such event.

                      f. Optionee understands that the certificate evidencing
the Securities will be imprinted with a legend which prohibits the transfer of
the Securities without the consent

                                       2.
<PAGE>   15
of the Commissioner of Corporations of California. Optionee has read the
applicable Commissioner's Rules with respect to such restriction, a copy of
which is attached.

                                               Signature of Optionee:

                                               ---------------------------------
                                               Date:                , 19
                                                      --------------    --

                                       3.
<PAGE>   16
                                  ATTACHMENT 1
              STATE OF CALIFORNIA - CALIFORNIA ADMINISTRATIVE CODE

         Title 10. Investment - Chapter 3. Commissioner of Corporations

  260.141.11: Restriction on Transfer. (a) The issuer of any security upon which
a restriction on transfer has been imposed pursuant to Sections 260.102.6,
260.141.10 or 260.534 shall cause a copy of this section to be delivered to each
issuee or transferee of such security at the time the certificate evidencing the
security is delivered to the issuee or transferee.

  (b) It is unlawful for the holder of any such security to consummate a sale or
transfer of such security, or any interest therein, without the prior written
consent of the Commissioner (until this condition is removed pursuant to Section
260.141.12 of these rules), except:

        (1) to the issuer;

        (2) pursuant to the order or process of any court;

        (3) to any person described in Subdivision (i) of Section 25102 of the
Code or Section 260.105.14 of these rules;

        (4) to the transferor's ancestors, descendants or spouse, or any
custodian or trustee for the account of the transferor or the transferor's
ancestors, descendants, or spouse; or to a transferee by a trustee or custodian
for the account of the transferee or the transferee's ancestors, descendants or
spouse;

        (5) to holders of securities of the same class of the same issuer;

        (6) by way of gift or donation inter vivos or on death;

        (7) by or through a broker-dealer licensed under the Code (either acting
as such or as a finder) to a resident of a foreign state, territory or country
who is neither domiciled in this state to the knowledge of the broker-dealer,
nor actually present in this state if the sale of such securities is not in
violation of any securities law of the foreign state, territory or country
concerned;

        (8) to a broker-dealer licensed under the Code in a principal
transaction, or as an underwriter or member of an underwriting syndicate or
selling group;

        (9) if the interest sold or transferred is a pledge or other lien given
by the purchaser to the seller upon a sale of the security for which the
Commissioner's written consent is obtained or under this rule not required;

        (10) by way of a sale qualified under Sections 25111, 25112, 25113 or
25121 of the Code, of the securities to be transferred, provided that no order
under Section 25140 or subdivision (a) of Section 25143 is in effect with
respect to such qualification;

        (11) by a corporation to a wholly owned subsidiary of such corporation,
or by a wholly owned subsidiary of a corporation to such corporation;

        (12) by way of an exchange qualified under Section 25111, 25112 or 25113
of the Code, provided that no order under Section 25140 or subdivision (a) of
Section 25143 is in effect with respect to such qualification;

        (13) between residents of foreign states, territories or countries who
are neither domiciled nor actually present in this state;

        (14) to the State Controller pursuant to the Unclaimed Property Law or
to the administrator of the unclaimed property law of another state; or

        (15) by the State Controller pursuant to the Unclaimed Property Law or
by the administrator of the unclaimed property law of another state if, in
either such case, such person (i) discloses to potential purchasers at the sale
that transfer of the securities is restricted under this rule, (ii) delivers to
each purchaser a copy of this rule, and (iii) advises the Commissioner of the
name of each purchaser;

        (16) by a trustee to a successor trustee when such transfer does not
involve a change in the beneficial ownership of the securities;

        (17) by way of an offer and sale of outstanding securities in an issuer
transaction that is subject to the qualification requirement of Section 25110 of
the Code but exempt from that qualification requirement by subdivision (f) of
Section 25102; provided that any such transfer is on the condition that any
certificate evidencing the security issued to such transferee shall contain the
legend required by this section.

        (c) The certificates representing all such securities subject to such a
restriction on transfer, whether upon initial issuance or upon any transfer
thereof, shall bear on their face a legend, prominently stamped or printed
thereon in capital letters of not less than 10-point size, reading as follows:

      "IT IS UNLAWFUL TO CONSUMMATE A SALE OR TRANSFER OF THIS SECURITY, OR ANY
      INTEREST THEREIN, OR TO RECEIVE ANY CONSIDERATION THEREFOR, WITHOUT THE
      PRIOR WRITTEN CONSENT OF THE COMMISSIONER OF CORPORATIONS OF THE STATE OF
      CALIFORNIA EXCEPT AS PERMITTED IN THE COMMISSIONER'S RULES."

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