[WSGR LETTERHEAD]

                                                                     EXHIBIT 5.1


International Network Services
1213 Innsbruck Drive
Sunnyvale, CA 94089

     Re:  REGISTRATION STATEMENT ON FORM S-1
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Ladies and Gentlemen:

    We have examined the Registration Statement on Form S-1 filed by you with 
the Securities and Exchange Commission on July 31, 1996 (Registration No. 
333-9287), as amended (the "Registration Statement"), in connection with the 
registration under the Securities Act of 1933, as amended, of up to 2,875,000 
shares of your Common Stock, no par value per share (the "Shares"). The Shares 
include an over-allotment option granted to the underwriters of the offering to 
purchase 375,000 shares. We understand that the Shares are to be sold to the 
underwriters of the offering for resale to the public as described in the 
Registration Statement. As your legal counsel, 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.

    It is our opinion that, upon completion of the proceedings being taken or 
contemplated by us, as your counsel, to be taken prior to the issuance of the 
Shares, including the proceedings being taken in order to permit such 
transaction to be carried out in accordance with applicable state securities 
laws, the Shares, when issued and sold in the manner described in the 
Registration Statement and in accordance with the resolutions adopted by the 
Board of Directors of the Company, 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 the Prospectus constituting a part thereof, 
and any amendments thereto.

                                 Very truly yours,

                                 WILSON SONSINI GOODRICH & ROSATI
                                 Professional Corporation

                                 /s/ Wilson Sonsini Goodrich & Rosati