EXHIBIT 5

                              OPINION RE LEGALITY


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[GRAY CARY WARE & FREIDENRICH LETTERHEAD]

                                January 18, 1995

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 CERTAIN INDIVIDUAL STOCK
                 OPTION AGREEMENTS, THE SECOND AMENDED AND RESTATED 1981
                 EMPLOYEE STOCK PURCHASE PLAN AND 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
1,903,229 shares of the Common Stock, $0.001 par value, of the Company which
may be issued pursuant to the exercise of options and purchase rights granted
under the 37 individual Metrologix, Inc. Employee Stock Option Agreements
assumed by KLA Instruments Corporation (the "Agreements"), the KLA Instruments
Corporation Second Amended and Restated 1981 Employee Stock Purchase Plan and
the 1982 Stock Option Plan (collectively the "Plans").

         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.


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Securities and Exchange Commission
Page 2


         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 1,903,229
shares of Common Stock which may be issued upon exercise of options and
purchase rights granted under the Agreements and the Plans 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 Agreements and
the Plans, 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

                                         GRAY CARY WARE & FREIDENRICH
                                         A Professional Corporation


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