POWER OF ATTORNEY
        Know all by these presents, that the undersigned hereby constitutes and
appoints each of WILLIAM D. YOUNG, ALFRED G. MERRIWEATHER and KATHY L. HIBBS,
signing individually, the undersigned's true and lawful attorneys-in fact and
agents to:
                (1)     execute for and on behalf of the undersigned, an
        officer, director or holder of 10% of more of a registered class of
        securities of VIROLOGIC, INC. (the "Company"), Forms 3, 4 and 5 in
        accordance with Section 16(a) of the Securities Exchange Act of 1934, as
    &nb
sp;   amended (the "Exchange Act") and the rules thereunder;
                (2)     do and perform any and all acts for and on behalf of the
        undersigned that may be necessary or desirable to complete and execute
        such Form 3, 4 or 5, complete and execute any amendment or amendments
        thereto, and timely file such forms or amendments with the United States
        Securities and Exchange Commission and any stock exchange or similar
        authority; and
                (3)     take any other action of any nature whatsoever in
        connection with the foregoing which, in the opinion of such
  
;      attorney-in-fact, may be of benefit, in the best interest of, or legally
        required by, the undersigned, it being understood that the documents
        executed by such attorney-in-fact on behalf of the undersigned pursuant
        to this Power of Attorney shall be in such form and shall contain such
        terms and conditions as such attorney-in-fact may approve in such
        attorney-in-fact's discretion.
        The undersigned hereby grants to each such attorney-in-fact full power
and authority to do and perform any and every act and thing whatsoever
requisite, necessary, or proper to be done in the exercise of any of the rights
and powers herein granted, as fully to all intents and purposes as the
undersigned might or could do if personally present, with full p
ower of
substitution or revocation, hereby ratifying and confirming all that such
attorney-in-fact, or such attorney-in-fact's substitute or substitutes, shall
lawfully do or cause to be done by virtue of this power of attorney and the
rights and powers herein granted. The undersigned acknowledges that the
foregoing attorneys-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Company assuming, any of the
undersigned's responsibilities to comply with Section 16 of the Exchange Act.
        This Power of Attorney shall remain in full force and effect until the
earliest to occur of (a) the undersigned is no longer required to file Forms 3,
4 and 5 with respect to the undersigned's holdings of and transactions in
securities issued by the Company, (b) revocation by the undersigned in a signed
writing delivered to the foregoing attorneys-in-fact or (c) as to any
attorney-in-fact individually, until
 such attorney-in-fact shall no longer be
employed by the Company.
        IN WITNESS WHEREOF, the undersigned has cause this Power of Attorney to
be executed as of this 16th day of December, 2004.
                                                     /s/ John D. Mendlein
                                                     ---------------------------
                   
                                  John D. Mendlein