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                                                                     EXHIBIT 5.1

                [LETTERHEAD OF WILSON SONSINI GOODRICH & ROSATI]


                                  June 4, 1999

Silicon Valley Group, Inc.
101 Metro Drive
San Jose, California 95110

        RE:  REGISTRATION STATEMENT ON FORM S-8

Ladies and Gentlemen:

        We have examined the Registration Statement on Form S-8 (the
"Registration Statement") to be filed by Silicon Valley Group, Inc., a Delaware
corporation (the Registrant" or "you"), with the Securities and Exchange
Commission on or about June 4, 1999 in connection with the registration under
the Securities Act of 1933, as amended ( the "1933 Act"), of the 1998
Non-Statutory Stock Option Plan (as to 1,000,000 shares), the 1996 Stock Plan
(as to 1,500,000 shares) and the 1996 Employee Stock Purchase Plan (as to
750,000 shares) (collectively, the "Plans" and the "Shares" as appropriate). As
legal counsel, we reviewed the actions taken and proposed to be taken by you in
connection with the proposed sale and issuance of the Shares by the Registrant
under the Plan.

        It is our opinion that, upon completion of the actions being taken, or
contemplated by us as your counsel to be taken by you prior to the issuance of
the Shares pursuant to the Registration Statement, the Plan, and upon completion
of the actions being taken in order to permit such transactions to be carried
out in accordance with the securities laws of the various states where required,
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 appearing in the
Registration Statement, including any Prospectus constituting a part thereof,
and any amendments thereto. This opinion may be incorporated by reference in any
abbreviated registration statement filed pursuant to Item E under the general
instructions to Form S-8 under the Securities Act of 1933 with respect to the
Registration Statement.

                                        Very truly yours,

                                        WILSON SONSINI GOODRICH & ROSATI
                                        Professional Corporation

                                        /s/ Wilson Sonsini Goodrich & Rosati