<PAGE>   1
                                                                     EXHIBIT 4.9

                                    WARRANT

THE SECURITIES PRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE SECURITIES
ACT OF 1933. SUCH SECURITIES AND ANY SECURITIES OR SHARES ISSUED HEREUNDER MAY
NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION
THEREFROM UNDER SAID ACT. COPIES OF THE AGREEMENT COVERING THE PURCHASE OF
THESE SECURITIES AND RESTRICTING THEIR TRANSFER OR SALE MAY BE OBTAINED AT NO
COST BY WRITTEN REQUEST MADE BY THE HOLDER OF RECORD HEREOF TO THE SECRETARY OF
THE COMPANY AT ITS PRINCIPAL EXECUTIVE OFFICES.

No. WA-__                                      Warrant to Purchase ______ Shares
                                               Series A Preferred Stock (subject
                                                         to adjustment)

                  WARRANT TO PURCHASE SERIES A PREFERRED STOCK

                                       OF

                                VIROLOGIC, INC.

                            VOID AFTER MAY 30, 2001

     This certifies that, for value received, ______________, or registered
assigns ("Holder") is entitled, subject to the terms set forth below, to
purchase from VIROLOGIC, INC. (the "Company"), a Delaware corporation, up to
______ shares of the Series A Preferred Stock of the Company, as constituted on
May 23, 1996 (the "Warrant Issue Date"), upon surrender hereof, at the principal
office of the Company referred to below, with the subscription form attached
hereto duly executed, and simultaneous payment therefor in lawful money of the
Unites States or otherwise as hereinafter provided, at the Exercise Price as set
forth in Section 2 below. The number, character and Exercise Price of such
shares of Series A Preferred Stock are subject to adjustment as provided below.
The term "Warrant" as used herein shall include this Warrant, which is one of a
series of warrants issued for the Series A Preferred Stock of the Company, and
any warrants delivered in substitution or exchange therefor as provided herein.

     This Warrant is issued in connection with the transactions described in
that certain Series A Preferred Stock Purchase Agreement between the Company and
the Investors described therein, dated as of May 23, 1996 (the "Purchase
Agreement").

     1.   Term of Warrant. Subject to the terms and conditions set forth
herein, this Warrant shall be exercisable, in whole or in part, during the term
commencing on the Warrant Issue Date


                                      -1-
<PAGE>   2
and ending at 5:00 p.m., Pacific standard time, on May 30, 2001, and shall be
void thereafter.

     2.   Exercise Price. The Exercise Price at which this Warrant may be
exercised shall be $1.84 per share of Series A Preferred Stock, as adjusted from
time to time pursuant to Section 11 hereof.

     3.   Vesting of Warrant. Effective as of the Warrant Issue Date, this
Warrant is exercisable with respect to ______ shares of Series A Preferred Stock
of the Company. Thereafter, this Warrant shall automatically become exercisable,
effective upon the Second Closing and each Option Closing (as such terms are
defined in Section 1 of the Purchase Agreement), if any, with respect to an
additional number of shares of Series A Preferred Stock equal to fifteen percent
(15%) of the Series A Preferred Stock sold and issued at the Second Closing and
each Option Closing, if any; provided, however, that this Warrant shall in no
event be exercisable for more than an aggregate of _______ shares of Series A
Preferred Stock of the Company (subject to adjustment as hereinafter provided).

     4.   Exercise of Warrant.

     (a)  The purchase rights represented by this Warrant are exercisable by the
Holder in whole or in part, at any time, or from time to time, during the term
hereof as described in Section 1 above, by the surrender of this Warrant and the
Notice of Exercise annexed hereto duly completed and executed on behalf of the
Holder, at the office of the Company (or such other office or agency of the
Company as it may designate by notice in writing to the Holder at the address of
the Holder appearing on the books of the Company), upon payment (i) in cash or
by check acceptable to the Company, (ii) by cancellation by the Holder of
indebtedness of the Company to the Holder, or (iii) by a combination of (i) and
(ii), of the purchase price of the shares to be purchased.

     (b)  This Warrant shall be deemed to have been exercised immediately prior
to the close of business on the date of its surrender for exercise as provided
above, and the person entitled to receive the shares of Series A Preferred Stock
issuable upon such exercise shall be treated for all purposes as the holder of
record of such shares as of the close of business on such date. As promptly as
practicable on or after such date and in any event within ten (10) days
thereafter, the Company at its expense shall issue and deliver to the person or
persons entitled to receive the same a certificate or certificates for the
number of shares issuable upon such exercise. In the event that this Warrant is
exercised in part, the Company at its expense will execute and deliver a new
Warrant of like tenor exercisable for the number of shares for which this
Warrant may then be exercised.

                                      -2-
<PAGE>   3
     (c)  Notwithstanding any provisions herein to the contrary, if the fair
market value of one share of Series A Preferred Stock is greater than the
Exercise Price (at the date of calculation as set forth below), in lieu of
exercising this Warrant for cash, the Holder may elect to receive shares equal
to the value (as determined below) of this Warrant (or the portion thereof
being cancelled) by surrender of this Warrant at the principal office of the
Company together with the properly endorsed Notice of Exercise and notice of
such election in which event the Company shall issue to the Holder a number of
shares of Series A Preferred Stock computed using the following formula:

                                 Y (A-B)
                               ----------
                         X  =       A

     Where     X =  the number of shares of Series A Preferred Stock to be
                    issued to the Holder

               Y =  the number of shares of Series A Preferred Stock purchasable
                    under the Warrant or, if only a portion of the Warrant is
                    being exercised, the portion of the Warrant being canceled
                    (at the date of such calculation)

               A =  the fair market value of one share of the Company's Series A
                    Preferred Stock (at the date of such calculation)

               B =  Exercise Price (as adjusted to the date of such calculation)

For purposes of the above calculation, fair market value of one share of Series
A Preferred Stock shall be determined by the Company's Board of Directors in
good faith; provided, however, that where there exists a public market for the
Company's Common Stock at the time of such exercise, the fair market value per
share shall be the product of (i) the average of the closing bid and asked
prices of the Common Stock quoted in the Over-The-Counter Market Summary or the
last reported sale price of the common Stock or the closing price quoted on The
Nasdaq National Market or on any exchange on which the Common Stock is listed,
whichever is applicable, as published in the Western Edition of The Wall Street
Journal for the five (5) trading days prior to the date of determination of
fair market value and (ii) the number of shares of Common Stock into which each
share of Series A Preferred Stock is convertible at the time of such exercise.
Notwithstanding the foregoing, in the event the Warrant is exercised in
connection with the Company's initial public offering of Common Stock, the fair
market value per share shall be the product of (i) the per share offering price
to the public of the Company's initial public offering, and (ii) the

                                      -3-


<PAGE>   4
number of shares of Common Stock into which each share of Series A Preferred
Stock is convertible at the time of such exercise.

      (d)   No fractional shares or scrip representing fractional shares shall
be issued upon the exercise of this Warrant. In lieu of any fractional share to
which the Holder would otherwise be entitled, the Company shall make a cash
payment equal to the Exercise Price multiplied by such fraction.

      5.    Replacement of Warrant. On receipt of evidence reasonably
satisfactory to the Company of the loss, theft, destruction or mutilation of
this Warrant and, in the case of loss, theft or destruction, on delivery of an
indemnity agreement reasonably satisfactory in form and substance to the
Company or, in case of mutilation, on surrender and cancellation of this
Warrant, the Company at its expense shall execute and deliver, in lieu of this
Warrant, a new warrant of like tenor and amount.

      6.    Rights of Stockholders. Subject to Sections 9 and 11 of this
Warrant, the Holder shall not be entitled to vote or receive dividends or be
deemed the holder of the Series A Preferred Stock to which this Warrant relates
or any other securities of the Company that may at any time be issuable on the
exercise hereof for any purpose.

      7.    Transfer of Warrant.

      (a)   Warrant Register. The Company will maintain a register (the "Warrant
Register") containing the names and addresses of the Holder or Holders. Any
Holder of this Warrant or any portion thereof may change his/her address as
shown on the Warrant Register by written notice to the Company requesting such
change. Any notice or written communication required or permitted to be given
to the Holder may be delivered or given my mail to such Holder as shown on the
Warrant Register and at the address shown on the Warrant Register. Until this
Warrant is transferred on the Warrant Register of the Company, the Company may
treat the Holder as shown on the Warrant Register as the absolute owner of
this Warrant for all purposes, notwithstanding any notice to the contrary.

      (b)   Warrant Agent. The Company may, by written notice to the Holder,
appoint an agent for the purpose of maintaining the Warrant Register referred to
in Section 7(a) above, issuing the Series A Preferred Stock or other securities
then issuable upon the exercise of this Warrant, exchanging this Warrant,
replacing this Warrant, or any or all of the foregoing. Thereafter, any such
registration, issuance, exchange, or replacement, as the case may be, shall be
made at the office of such agent.

      (c)   Transferability and Nonnegotiability of Warrant. This Warrant may
not be transferred or assigned (i) except in its


                                      -4-
<PAGE>   5
entirety and (ii) without compliance with all applicable federal and state
securities laws by the transferor and the transferee (including the delivery of
investment representation letters reasonably satisfactory to the Company, if
such are requested by the Company), and then only against receipt of an
agreement of the transferee to comply with the provisions of this Section 7(c)
with respect to any resale or other disposition of this Warrant. Subject to the
provisions of this Warrant with respect to compliance with the Securities Act of
1933, as amended (the "Act"), title to this Warrant may be transferred by
endorsement (by the Holder executing the Assignment Form annexed hereto) and
delivery in the same manner as a negotiable instrument transferable by
endorsement and delivery.

      (d)   Exchange of Warrant Upon a Transfer. On surrender of this Warrant
for exchange, properly endorsed on the Assignment Form and subject to the
provisions of this Warrant with respect to compliance with the Act and with the
limitations on assignments and transfers and contained in this Section 7, the
Company at its expense shall issue to or on the order of the Holder a new
warrant or warrants of like tenor, in the name of the Holder or as the Holder
(on payment by the Holder of any applicable transfer taxes) may direct, for the
number of shares issuable upon exercise hereof.

      (e)   Compliance with Securities Laws.

      (i)   The Holder of this Warrant, by acceptance hereof, acknowledges that
this Warrant and the shares of Series A Preferred Stock or Common Stock to be
issued upon exercise hereof or conversion thereof are being acquired solely for
the Holder's own account and not as a nominee for any other party, and for
investment, and that the Holder will not offer, sell or otherwise dispose of
this Warrant or any shares of Series A Preferred Stock or Common Stock to be
issued upon exercise hereof or conversion thereof except under circumstances
that will not result in a violation of the Act or any state securities laws.
Upon exercise of this Warrant, the Holder shall, if requested by the Company,
confirm in writing, in a form satisfactory to the Company, that the shares of
Series A Preferred Stock or Common Stock so purchased are being acquired solely
for the Holder's own account and not as a nominee for any other party, for
investment, and not with a view toward distribution or resale.

      (ii)  This Warrant and all shares of Series A Preferred Stock or Common
Stock issued upon exercise hereof or conversion thereof shall be stamped or
imprinted with a legend in substantially the following form (in addition to any
legend required by state securities laws):

      THE SECURITIES REPRESENTED HEREBY HAVE NOT BEEN REGISTERED UNDER THE
      SECURITIES ACT OF 1933. SUCH SECURITIES AND ANY SECURITIES OR SHARES
      ISSUED HEREUNDER



                                      -5-
<PAGE>   6
     MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR AN
EXEMPTION THEREFROM UNDER SAID ACT. COPIES OF THE AGREEMENT COVERING THE
PURCHASE OF THESE SECURITIES AND RESTRICTING THEIR TRANSFER OR SALE MAY BE
OBTAINED AT NO COST BY WRITTEN REQUEST MADE BY THE HOLDER OF RECORD HEREOF TO
THE SECRETARY OF THE COMPANY AT ITS PRINCIPAL EXECUTIVE OFFICES.

     8. Reservation of Stock. The Company covenants that during the term this
Warrant is exercisable, the Company will reserve from its authorized and
unissued Series A Preferred Stock a sufficient number of shares to provide for
the issuance of Series A Preferred Stock upon the exercise of this Warrant (and
shares of its Common Stock for issuance on conversion of such Series A
Preferred Stock) and, from time to time, will take all  steps necessary to amend
its Certificate of Incorporation (the "Certificate") to provide sufficient
reserves of shares of Series A Preferred Stock issuable upon exercise of the
Warrant (and shares of its Common Stock for issuance on conversion of such
Series A Preferred Stock). The Company further covenants that all shares that
may be issued upon the exercise of rights represented by this Warrant, upon
exercise of the rights represented by this Warrant and payment of the Exercise
Price, all as set forth herein, will be free from all taxes, liens and charges
in respect of the issue thereof (other than taxes in respect of any transfer
occurring contemporaneously or otherwise specified herein). The Company agrees
that its issuance of this Warrant shall constitute full authority to its
officers who are charged with the duty of executing stock certificates to
execute and issue the necessary certificates for shares of Series A Preferred
Stock upon the exercise of this Warrant.

     9. Notices.

     (a) Whenever the Exercise Price or number of shares purchasable hereunder
shall be adjusted pursuant to Section 11 hereof, the Company shall issue a
certificate signed by its Chief Financial Officer setting forth, in reasonable
detail, the event requiring the adjustment, the amount of the adjustment, the
method by which such adjustment was calculated, and the Exercise Price and
number of shares purchasable hereunder after giving effect to such adjustment,
and shall cause a copy of such certificate to be mailed (by first-class mail,
postage prepaid) to the Holder of this Warrant.

     (b) In case:

          (i) the Company shall take a record of the holders of its Series A
Preferred Stock or Common Stock (or other stock or securities at the time
receivable upon the exercise or conversion of this Warrant) for the purpose of
entitling them to receive any dividend or other distribution, or any right to
subscribe for or purchase any shares of stock of any


                                      -6-
<PAGE>   7

     class or any other securities, or to receive any other right, or

          (ii)  of any capital reorganization of the Company, any
     reclassification of the capital stock of the Company, any consolidation or
     merger of the Company with or into another corporation, or any conveyance
     of all or substantially all of the assets of the Company to another
     corporation, or

          (iii) of any voluntary dissolution, liquidation or winding-up of the
     Company.

then, and in each such case, the Company will mail or cause to be mailed to the
Holder or Holders a notice specifying, as the case may be, (A) the date on
which a record is to be taken for the purpose of such dividend, distribution or
right, and stating the amount and character of such dividend, distribution or
right, or (B) the date on which such reorganization, reclassification,
consolidation, merger, conveyance, dissolution, liquidation or winding-up is to
take place, and the time, if any is to be fixed, as of which the holders of
record of Series A Preferred stock or Common Stock (or such stock or securities
at the time receivable upon the exercise of this Warrant) shall be entitled to
exchange their shares of Series A Preferred Stock or Common Stock (or such
other stock or securities) for securities or other property deliverable upon
such reorganization, reclassification, consolidation, merger, conveyance,
dissolution, liquidation or winding up. Such notice shall be mailed at least
fifteen (15) days prior to the date therein specified.

     (c)  All such notices, advices and communications shall be deemed to have
been received (i) in the case of personal delivery, on the date of such
delivery and (ii) in the case of mailing, on the third business day following
the date of such mailing.

     10.  Amendments. This Warrant and any term hereof may be changed, waived,
discharged or terminated only by an instrument in writing signed by the party
against which enforcement of such change, waiver, discharge or termination is
sought.

     11.  Adjustments. The Exercise Price and the number of shares purchasable
hereunder are subject to adjustment from time to time as follows:

     11.1  Conversion or Redemption of Series a Preferred Stock. Should all of
the Company's Series A Preferred Stock be, or if outstanding would be, at any
time prior to the expiration of this Warrant or any portion thereof, redeemed
or converted into shares of the Company's Common Stock in accordance with
Section 4(b) of the Certificate, then this Warrant shall immediately become
exercisable for that number of shares of the Company's Common Stock equal to
the number of shares of the

                                      -7-
<PAGE>   8
Common Stock that would have been received if this Warrant had been exercised
in full and the Series A Preferred Stock received thereupon and been
simultaneously converted immediately prior to such event, and the Exercise
Price shall be immediately adjusted to equal the quotient obtained by dividing
(x) the aggregate Exercise Price of the maximum number of shares of Series A
Preferred Stock for which this Warrant was exercisable immediately prior to
such conversion or redemption, by (y) the number of shares of Common Stock for
which this Warrant is exercisable immediately after such conversion or
redemption. For purposes of the foregoing, the "Certificate" shall mean the
Certificate of  Incorporation of the Company as amended and/or restated and
effective immediately prior to the redemption or conversion of all of the
Company's Series A Preferred Stock.

     11.2 Merger, Sale of Assets, etc. If at any time while this Warrant, or
any portion thereof, is outstanding and unexpired there shall be (a) a
reorganization (other than a combination, reclassification, exchange or
subdivision of shares otherwise provided for herein), (b) a merger or
consolidation of the Company with or into another corporation in which the
Company is not the surviving entity, or a reverse triangular merger in which
the Company is the surviving entity but the shares of the Company's capital
stock outstanding immediately prior to the merger are converted by virtue of
the merger into other property, whether in the form of securities, cash or
otherwise, or (c) a sale or transfer of the Company's properties and assets as,
or substantially as, an entirety to any other person, then the Company shall
provide the holder of this Warrant with not less than thirty (30) days' prior
written notice of such event and an opportunity to exercise this Warrant
effective upon the consummation of such event, so that, as a part of such
reorganization, merger, consolidation, sale or transfer, the holder of this
Warrant shall be entitled to receive upon exercise of this Warrant the number
of shares of stock or other securities or property of the successor corporation
resulting from such reorganization, merger, consolidation, sale or transfer that
a holder of the shares deliverable upon exercise of this Warrant would have
been entitled to receive in such reorganization, consolidation, merger, sale or
transfer. The Company shall not effect any such consolidation, merger, sale,
transfer or other disposition unless prior to or simultaneously with the
consummation thereof the successor corporation (if other than the Company)
resulting from such consolidation or merger, or the corporation purchasing or
otherwise acquiring such assets or other appropriate corporation or entity
shall agree to deliver to the holder of the Warrant, upon its exercise and
payment of the Exercise Price then in effect, such shares of stock, securities
or assets as, in accordance with the foregoing provisions, such holder may be
entitled to purchase.

     11.3 Reclassification, etc. If the Company, at any time while this
Warrant, or any portion thereof, remains outstanding

                                      -8-
<PAGE>   9
and unexpired, by reclassification of securities or otherwise, shall change any
of the securities as to which purchase rights under this Warrant exist into the
same or a different number of securities of any other class or classes, this
Warrant shall thereafter represent the right to acquire such number and kind of
securities as would have been issuable as the result of such change with
respect to the securities that were subject to the purchase rights under this
Warrant immediately prior to such reclassification or other change and the
Exercise Price therefor shall be appropriately adjusted, all subject to further
adjustment as provided in this Section 11. No adjustment shall be made pursuant
to this Section 11.3, upon any conversion or redemption of the Series A
Preferred Stock which is the subject of Section 11.1.

     11.4 Split, Subdivision or Combination of Shares. If the Company at any
time while this Warrant, or any portion thereof, remains outstanding and
unexpired shall split, subdivide or combine the securities as to which purchase
rights under this Warrant exist, into a different number of securities of the
same class, the Exercise Price for such securities shall be proportionately
decreased in the case of a split or subdivision or appropriately increased in
the case of a combination.

     11.5 Adjustments for Dividends in Stock or Other Securities or Property. If
while this Warrant, or any portion hereof, remains outstanding and unexpired the
holders of the securities as to which purchase rights under this Warrant exist
at the time shall have received, or, on or after the record date fixed for the
determination of eligible Stockholders, shall have become entitled to receive,
without payment therefor, other or additional stock or other securities or
property (other than cash) of the Company by way of dividend, then and in each
case, this Warrant shall represent the right to acquire, in addition to the
number of shares of the security receivable upon exercise of this Warrant, and
without payment of any additional consideration therefor, the amount of such
other or additional stock or other securities or property (other than cash) of
the Company that such holder would hold on the date of such exercise had it been
the holder of record of the security receivable upon exercise of this Warrant on
the date hereof and had thereafter, during the period from the date hereof to
and including the date of such exercise, retained such shares and/or all other
additional stock available by it as aforesaid during such period, giving effect
to all adjustments called for during such period by the provisions of this
Section 11.

     11.6 Certificate as to Adjustments. Upon the occurrence of each adjustment
or readjustment pursuant to this Section 11, the Company at its expense shall
promptly compute such adjustment or readjustment in accordance with the terms
hereof and furnish to each Holder of this Warrant a certificate setting forth
such adjustment or readjustment and showing in detail the facts upon which such
adjustment or readjustment is based. The

                                      -9-
<PAGE>   10

Company shall, upon the written request, at any time, of any such Holder,
furnish or cause to be furnished to such Holder a like certificate setting
forth: (a) such adjustments and readjustments; (b) the Exercise Price at the
time in effect; and (c) the number of shares and the amount, if any, of other
property that at the time would be received upon the exercise of the Warrant.

     11.7  No Impairment. The Company will not, by any voluntary action, avoid
or seek to avoid the observance or performance of any of the terms to be
observed or performed hereunder by the Company, but will at all times in good
faith assist in the carrying out of all the provisions of this Section 11 and
in the taking of all such action as may be necessary or appropriate in order to
protect the rights of the Holders of this Warrant against impairment.

     12.  Registration Rights. Upon exercise of this Warrant, the Holder shall
have and be entitled to exercise, together with all other holders of
Registrable Securities possessing registration rights under that certain
Investors' Rights Agreement, of even date herewith, between the Company and the
parties who have executed the counterpart signature pages thereto or are
otherwise bound thereby (the "Investors' Rights Agreement"), the rights of
registration granted under the Investors' Rights Agreement to Registrable
Securities (with respect to the Shares issued on exercise of this Warrant). By
its receipt of this Warrant, Holder agrees to be bound by the Investors' Rights
Agreement upon exercise of this Warrant as a party thereto.

     13.  Miscellaneous.

     (a)  Successors. All the covenants and provisions hereof by or for the
benefit of the Company or the Holder shall bind and inure to the benefit of
their respective successors and assigns hereunder.

     (b)  Governing Law. This Warrant shall be deemed to be a contract made
under the laws of the State of California and for all purposes shall be
construed in accordance with the laws of said State.

     (c)  Attorneys Fees in the Event of a Dispute. In the event of any action
at law, suit in equity or arbitration proceeding in relation to this Warrant or
any Series A Preferred Stock issued or to be issued hereunder, the prevailing
party or parties, shall be paid by the other party or parties a reasonable sum
for attorneys' fees and expenses of such prevailing party or parties.

     (d)  Saturdays, Sundays, Holidays. If the last or appointed day for the
taking of any action or the expiration of any right required or granted herein
shall be a Saturday or a Sunday or shall be a legal holiday in the State of
California,

                                      -10-
<PAGE>   11

then such actions may be taken or such right may be exercised on the next
succeeding day not a legal holiday.

     IN WITNESS WHEREOF, VIROLOGIC, INC. has caused this Warrant to be executed
by its officers thereunto duly authorized.

     Dated: May 24, 1996.

                                        VIROLOGIC, INC.


                                        By /s/ [SIGNATURE ILLEGIBLE]
                                           ------------------------------------


HOLDER:



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

<PAGE>   12
                               NOTICE OF EXERCISE

To: VIROLOGIC, INC.

      (1)   The undersigned hereby elects to purchase ______ shares of Series A
Preferred Stock of VIROLOGIC, INC., pursuant to the terms of the attached
Warrant, and tenders herewith payment of the purchase price for such shares in
full.

      (2)   In exercising this Warrant, the undersigned hereby confirms and
acknowledges that the shares of Series A Preferred Stock or the Common Stock to
be issued upon conversion thereof are being acquired solely for the account of
the undersigned and not as a nominee for any other party, or for investment,
and that the undersigned will not offer, sell or otherwise dispose of any such
shares of Series A Preferred Stock or Common Stock except under circumstances
that will not result in a violation of the Securities Act of 1933, as amended,
or any state securities laws.

      (3)   Please issue a certificate or certificates representing said shares
of Series A Preferred Stock in the name of the undersigned or in such other
name as is specified below:

                                              ----------------------------
                                                         (Name)


                                              ----------------------------
                                                         (Name)


      (4) Please issue a new Warrant for the unexercised portion of the
attached Warrant in the name of the undersigned or in such other name as is
specified below:


                                              ----------------------------
                                                         (Name)


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


<PAGE>   13
                                ASSIGNMENT FORM

      FOR VALUE RECEIVED, the undersigned registered owner of this Warrant
hereby sells, assigns and transfers unto the Assignee named below all of the
rights of the undersigned under the within Warrant, with respect to the number
of shares of Series A Preferred Stock (or Common Stock) set forth below:

<TABLE>
<CAPTION>
Name of Assignee       Address                              No. of Shares
----------------       -------                              -------------
<S>                    <C>                                  <C>










</TABLE>

and does hereby irrevocably constitute and appoint Attorney __________________
to make such transfer on the books of VIROLOGIC, INC., maintained for the
purpose, with full power of substitution in the premises.

      The undersigned also represents that, by assignment hereof, the Assignee
acknowledges that this Warrant and the shares of stock to be issued upon
exercise hereof or conversion thereof are being acquired for investment and
that the Assignee will not offer, sell or otherwise dispose of this Warrant or
any shares of stock to be issued upon exercise hereof or conversion thereof
except under circumstances which will not result in a violation of the
Securities Act of 1933, as amended, or any state securities laws. Further, the
Assignee has acknowledged that upon exercise of this Warrant, the Assignee
shall, if requested by the Company, confirm in writing, in a form satisfactory
to the Company, that the shares of stock so purchased are being acquired for
investment and not with a view toward distribution or resale.

      Dated:
            ------------------


                                              ----------------------------
                                                  (Signature of Holder)