EXHIBIT 4.1


                          [KLA-TENCOR CORPORATION LOGO]

                                  COMMON STOCK

                                [CUSIP PENDING]


INCORPORATED UNDER THE LAWS OF THE STATE OF DELAWARE

THIS CERTIFICATE IS TRANSFERABLE            SEE REVERSE FOR CERTAIN DESCRIPTIONS
 IN BOSTON, MA OR NEW YORK, NY



THIS CERTIFIES THAT

                    ----------------------------------------

IS THE OWNER OF

                    ----------------------------------------

            FULLY PAID AND NONASSESSABLE SHARES OF THE COMMON STOCK,
                               $.001 PAR VALUE OF

                             KLA-TENCOR CORPORATION

the transfer of which may be registered on the books maintained for such
purpose by or on behalf of the Corporation upon surrender of this
Certificate properly endorsed.  This Certificate is not valid until
countersigned by the Transfer Agent and registered by the Registrar.

        WITNESS the facsimile seal of the Corporation and the facsimile
signatures of its duly authorized officers.

Dated:
       -------------------

                                     [SEAL]


     ----------------------                             -----------------------
     SECRETARY                                          CHAIRMAN OF THE BOARD



Countersigned and registered:
        THE FIRST NATIONAL BANK OF BOSTON
             TRANSFER AGENT AND REGISTRAR

BY:               
    ------------------------------------
                    AUTHORIZED SIGNATURE

         This certificate also evidences and entitles the holder hereof to
certain Rights as set forth in an Amended and Restated Rights Agreement between
KLA Instruments Corporation and The First National Bank of Boston, as Rights
Agent, dated as of April 25, 1996 (as amended from time to time in accordance
with its terms, the "Rights Agreement"), the terms of which are incorporated
herein by reference and a copy of which is on file at the principal executive
office of KLA-Tencor Corporation. Under certain circumstances, as set forth in
the Rights Agreement, such rights will be evidenced by separate certificates
and will no longer be evidenced by this certificate. KLA-Tencor Corporation
will mail to the holder of this certificate a copy of the Rights Agreement
without charge after receipt by it of a written request therefor. Under certain
circumstances as provided in the Rights Agreement, Rights issued to or
beneficially owned by Acquiring Persons or their Associates or Affiliates (as
defined in the Rights Agreement) or any subsequent holder of such Rights will
be null and void and will no longer be transferrable.

        The following abbreviations, when used in the inscription on the face
of this certificate, shall be construed as though they were written out in full
according to applicable laws or regulations:

<TABLE>
        <S>                                            <C>
        TEN COM   --  as tenants in common              UNIF GIFT MIN ACT -- ...................Custodian...............
        TEN ENT   --  as tenants by the entireties                                 (Cust)                    (Minor) 
        JT TEN    --  as joint tenants with right of                         under Uniform Gifts to Minors
                      survivorship and not as tenants                        Act........................................
                      in common                                                                 (State)
                                                        UNIF TRF MIN ACT  -- .............Custodian (until age.........)
                                                                                 (Cust)
                                                                             ....................under Uniform Transfers
                                                                                    (Minor)
                                                                             to Minors Act..............................
                                                                                                   (State)
</TABLE>


    Additional abbreviations may also be used though not in the above list.


        FOR VALUE RECEIVED,___________________________hereby sell, assign and
transfer unto

PLEASE INSERT SOCIAL SECURITY OR OTHER
   IDENTIFYING NUMBER OF ASSIGNEE
- --------------------------------------

- --------------------------------------


_______________________________________________________________________________
 (PLEASE PRINT OR TYPEWRITE NAME AND ADDRESS, INCLUDING ZIP CODE, OF ASSIGNEE)

_______________________________________________________________________________

_______________________________________________________________________________

________________________________________________________________________ Shares
of the capital stock represented by the within Certificate, and do hereby
irrevocably constitute and appoint

______________________________________________________________________ Attorney
to transfer the said stock on the books of the within named Corporation
with full power of substitution in the premises.

Dated________________________


                                X_______________________________________________
  
                                X_______________________________________________
                                 THE SIGNATURE(S) TO THIS ASSIGNMENT MUST 
                                 CORRESPOND WITH THE NAME(S) AS WRITTEN UPON THE
                       NOTICE:   FACE OF THE CERTIFICATE IN EVERY PARTICULAR,
                                 WITHOUT ALTERATION OR ENLARGEMENT OR ANY
                                 CHANGE WHATEVER.

Signature(s) Guaranteed




By___________________________________
THE SIGNATURE(S) SHOULD BE GUARANTEED
BY AN ELIGIBLE GUARANTOR INSTITUTION
(BANKS, STOCKBROKERS, SAVINGS AND
LOAN ASSOCIATIONS AND CREDIT UNIONS
WITH MEMBERSHIP IN AN APPROVED
SIGNATURE GUARANTEE MEDALLION PROGRAM),
PURSUANT TO S.E.C. RULE 17Ad-15.