EXHIBIT 5
 
                              OPINION RE LEGALITY


                  (GRAY CARY WARE & FREIDENRICH LETTERHEAD)


                                                                  OUR FILE NO.
                                                                1110147-903201


                                 April 26, 1996
 
Securities and Exchange Commission
450 Fifth Street, N.W.
Washington, D.C. 20549
 
     RE:  KLA INSTRUMENTS CORPORATION -- REGISTRATION STATEMENT ON FORM S-8
        REGISTERING SHARES ISSUABLE UNDER THE 1982 STOCK OPTION PLAN
 
Ladies and Gentlemen:
 
     As legal counsel for KLA Instruments Corporation, a Delaware corporation
(the "Company"), we are rendering this opinion in connection with the
registration under the Securities Act of 1933, as amended, of up to 2,200,000
shares of the Common Stock, $0.001 par value, of the Company which may be issued
pursuant to the exercise of options granted under the 1982 Stock Option Plan
(the "Plan").
 
     We have examined all instruments, documents and records which we deemed
relevant and necessary for the basis of our opinion hereinafter expressed. In
such examination, we have assumed the genuineness of all signatures and the
authenticity of all documents submitted to us as originals and the conformity to
the originals of all documents submitted to us as copies.
 
     We are admitted to practice only in the State of California and we express
no opinion concerning any law other than the law of the State of California, the
corporation laws of the State of Delaware and the federal law of the United
States.
 
     As to matters of Delaware corporation law, we have based our opinion solely
upon our examination of such laws and the rules and regulations of the
authorities administering such laws, all as reported in standard, unofficial
compilations. We have not obtained opinions of counsel licensed to practice in
jurisdictions other than the State of California.
 
     Based on such examination, we are of the opinion that the 2,200,000 shares
of Common Stock which may be issued upon exercise of options granted under the
Plan are duly authorized shares of the Company's Common Stock, and, when issued
against payment of the purchase price therefor in accordance with the provisions
of the Plan, will be validly issued, fully paid and non-assessable.
 
     We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement referred to above and the use of our name wherever it
appears in said Registration Statement.
 
                                          Respectfully submitted,
 
                                          /s/ GRAY CARY WARE & FREIDENRICH
 
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                                          GRAY CARY WARE & FREIDENRICH
                                          A Professional Corporation