Prospectus Supplement #12                       Filed pursuant to Rule 424(b)(3)
(to prospectus dated November 17, 2000)               Registration No. 333-47150


                        MERCURY INTERACTIVE CORPORATION

           4.75% Convertible Subordinated Notes Due July 1, 2007 and
         Shares of Common Stock Issuable Upon Conversion of the Notes

                            ______________________


     This prospectus supplement relates to the resale by the holders of our
4.75% convertible subordinated notes due July 1, 2007 and the shares of our
common stock issuable upon the conversion of the notes.  You should read this
prospectus supplement in conjunction with the prospectus dated November 17,
2000, which is to be delivered with this prospectus supplement.

     The information in the table appearing under the heading "Selling Holders"
in the prospectus is amended by the addition of the information appearing in the
table below:



                                                    Principal
                                                 Amount of Notes                                              Common Stock
                                                   Beneficially     Common Stock Owned                         Owned After
                                                    Owned and          Prior to the            Common         Completion of
Name of Beneficial Owner                             Offered          Offering(1)(2)       Stock Offered      the Offering
------------------------                         --------------     ------------------     --------------     -------------
                                                                                                
EQAT Alliance Growth Investors.................   $   2,940,000                 26,427             26,427                --



(1) Includes common stock into which the notes are convertible.
(2) Assumes a conversion ratio of 8.9888 shares per $1,000 principal amount of
    notes and a cash payment in lieu of any fractional interest.


                    ________________________________________


     Investing in our common stock or the notes involves a high degree of risk.
Please carefully consider the "Risk Factors" beginning on page 3 of the
prospectus, as well as the "Risk Factors" section included in our recent reports
filed with the Securities and Exchange Commission.


     Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or passed upon the
adequacy or accuracy of THE prospectus or this prospectus supplement.  Any
representation to the contrary is a criminal offense.


           The date of this prospectus supplement is August 28, 2001.