Exhibit 5.1

                            MORRISON & FOERSTER LLP
                           San Francisco, California


                                February 3, 1999



XOOM.com, Inc.
300 Montgomery Street, Suite 300
San Francisco, California 94104

Gentlemen:

   At your request, we have examined the Registration Statement on Form S-8
executed by you on February 3, 1999, and to be filed with the Securities and
Exchange Commission (the "SEC") in connection with the registration under the
Securities Act of 1933, as amended, of an aggregate of 2,300,000 shares of your
common stock, $.0001 par value (the "Common Stock") which will be issuable under
the 1998 Stock Incentive Plan and the 1998 Employee Stock Purchase Plan (the
"Plans").

   As your counsel in connection with the Registration Statement, we have
examined the proceedings taken by you in connection with the adoption of the
Plans and the authorization of the issuance of the shares of Common Stock under
the Plans (the "Plan Shares") and such documents as we have deemed necessary to
render this opinion.

   Based upon the foregoing, it is our opinion that the Plan Shares, when issued
and outstanding pursuant to the terms of the Plans, will be validly issued,
fully paid and non-assessable shares of Common Stock.

   We consent to the use of this opinion as an exhibit to the Registration
Statement.

                            Very truly yours,

                            Morrison & Foerster LLP