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                                                                     EXHIBIT 5.1
                [LETTERHEAD OF WILSON SONSINI GOODRICH & ROSATI]


                                 March 21, 2001

VIVUS, Inc.
1172 Castro Street
Mountain View, CA 94040
(650) 934-5200

     RE:  REGISTRATION STATEMENT ON FORM S-8

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 March 21, 2001 (the
"Registration Statement") in connection with the registration under the
Securities Act of 1933, as amended, of recently authorized shares to be issued
under the 1994 Employee Stock Purchase Plan (as to 400,000 shares) (the "Plan"
and the "Shares" as appropriate). As your counsel in connection with this
transaction, we have examined the proceedings taken and are familiar with the
proceedings proposed to be taken by you in connection with the issuance and sale
of the Shares pursuant to the Plan.

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

     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 appearing in the
Registration Statement and any amendments thereto.

                                        Very truly yours,

                                        WILSON SONSINI GOODRICH & ROSATI
                                        Professional Corporation



                                        /s/ WILSON SONSINI GOODRICH & ROSATI