EXHIBIT 99.1

                                  CERTIFICATION

        Pursuant to Section 906 of the Public Company Accounting Reform and
Investor Protection Act of 2002 (18 U.S.C. Section 1350, as adopted), William D.
Young, the Chief Executive Officer of ViroLogic, Inc. (the "Company"), and Karen
J. Wilson, the Chief Financial Officer of the Company, each hereby certifies
that, to the best of his or her knowledge:

1. The Company's Quarterly Report on Form 10-Q for the period ended June 30,
2002, to which this Certification is attached as Exhibit 99.1 (the "Periodic
Report"), fully complies with the requirements of Section 13(a) or Section 15(d)
of the Securities Exchange Act of 1934, as amended; and

2. The information contained in the Periodic Report fairly presents, in all
material respects, the financial condition of the Company at the end of the
period covered by the Periodic Report and results of operations of the Company
for the period covered by the Periodic Report.

Dated:  August 12, 2002

 /s/ William D. Young                        /s/ Karen J. Wilson
- --------------------------                  --------------------------------
William D. Young                            Karen J. Wilson
Chief Executive Officer                     Chief Financial Officer