EXHIBIT 5.1

                              OPINION OF COUNSEL


May 29, 2001

Mercury Interactive Corporation
1325 Borregas Avenue
Sunnyvale, California 94089

     Re: Registration Statement on Form S-8
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Ladies and Gentlemen:

     We have examined the Registration Statement on Form S-8 to be filed by you
with the Securities and Exchange Commission on or about May 29, 2001 (the
"Registration Statement") in connection with the registration under the
Securities Act of 1933, as amended, of a total of 676,359 shares of your Common
Stock (the "Shares") reserved for issuance under the Freshwater Software, Inc.
1997 Stock Plan and 1998 Employee Stock Purchase Plan (the "Plans").  As legal
counsel for Mercury Interactive Corporation, we have examined the proceedings
taken and are familiar with the proceedings proposed to be taken by you in
connection with the sale and issuance of the Shares under the Plan.

     It is our opinion that, when issued and sold in the manner referred to in
the Plan and pursuant to the agreement which accompanies each grant under the
Plan, the Shares will be legally and validly issued, fully paid and
nonassessable.

     We consent to the use of this opinion as an exhibit to the Registration
Statement and further consent to the use of our name wherever it appears in the
Registration Statement and any amendments thereto.

                              Very truly yours,

                              GENERAL COUNSEL ASSOCIATES LLP


                              /s/ General Counsel Associates LLP