EXHIBIT 5.1





                                 March 7, 1997

KLA Instruments Corporation
160 Rio Robles
San Jose, CA 95134

         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 7, 1997 (the
"Registration Statement"), in connection with the registration under the
Securities Act of 1933, as amended, of (i) 1,600,000 shares of your Common
Stock reserved for issuance under the 1982 Stock Option Plan (the "Stock Plan")
and (ii) 800,000 shares of your Common Stock reserved for issuance under the
Second Restated 1981 Employee Stock Purchase Plan (the "Purchase Plan").  The
1,600,000 shares of Common Stock reserved under the Stock Plan and the 800,000
shares of Common Stock reserved under the Purchase Plan are referred to
collectively hereinafter as the "Shares," and the Stock Plan and the Purchase
Plan are referred to hereinafter collectively as the "Plans."  As your legal
counsel, we have examined the proceedings taken and proposed to be taken in
connection with the issuance, sale and payment of consideration for the Shares
to be issued under the Plans.

         It is our opinion that, when issued and sold in compliance with
applicable prospectus delivery requirements and in the manner referred to in
the Plans and pursuant to the agreements which accompany the Plans, the Shares
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.

                                                   Sincerely,

                                                WILSON SONSINI GOODRICH & ROSATI
                                                   Professional Corporation

                                            /s/ Wilson Sonsini Goodrich & Rosati