<PAGE>   1
          As filed with the Securities and Exchange Commission on August 7, 1998
                                                   Registration No. 333-________

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

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


                             KLA-TENCOR CORPORATION
             (Exact name of registrant as specified in its charter)

<TABLE>
<S>                                         <C>
       DELAWARE                                           04-2564110
(State of incorporation)                    (I.R.S. Employer Identification No.)
</TABLE>
                                 160 Rio Robles
                               San Jose, CA 95134
          (Address, including zip code, of principal executive offices)

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

                        RESTATED 1982 STOCK OPTION PLAN
                           (Full Titles of the Plans)

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

                                  LISA C. BERRY
                         VICE PRESIDENT, GENERAL COUNSEL
                             KLA-TENCOR CORPORATION
                                 160 Rio Robles
                               San Jose, CA 95134
                     (Name and address of agent for service)
                                 (408) 875-3000
          (Telephone number, including area code, of agent for service)

                                    Copy to:
                             JUDITH M. O'BRIEN, ESQ.
                        WILSON SONSINI GOODRICH & ROSATI
                            Professional Corporation
                               650 Page Mill Road
                        Palo Alto, California 94304-1050

================================================================================
                         CALCULATION OF REGISTRATION FEE
================================================================================

<TABLE>
<CAPTION>
                                                          Proposed Maximum           Proposed Maximum
 Title of Securities to be     Amount to be              Offering Price Per         Aggregate offering        Amount of Registration
        Registered              Registered                   Share(1)                    Price(1)                      Fee
---------------------------  ----------------------  -------------------------  ---------------------------   ----------------------
<S>                          <C>                          <C>                         <C>                     <C>
Common Stock, $.001              2,618,837                  $28.8125                    $75,455,241                 $22,865
par value, to be issued
upon exercise of options
granted under the
Restated 1982 Stock
Option Plan
Total                            2,618,837                  $28.8125                    $75,455,241                  $22,865
-----                            ---------                  --------                    -----------                  -------
</TABLE>

(1) The Proposed Maximum Offering Price Per Share was estimated in accordance
    with Rule 457(c) and Rule 457(h) under the Securities Act of 1933, as
    amended, (the "SECURITIES ACT") solely for the purpose of calculating the
    registration fee, based on the average between the high and low price of the
    Registrant's stock as reported in the Nasdaq National Market on August 3,
    1998. 

<PAGE>   2


                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         KLA-Tencor Corporation (the "REGISTRANT" or the "COMPANY") hereby
incorporates by reference in this registration statement the following
documents:

         (a)      The Registrant's Annual Report on Form 10-K for the fiscal
                  year ended June 30, 1997 (File No. 000-09992) pursuant to
                  Section 13(a) of the Securities Exchange Act of 1934, as
                  amended (the "Exchange Act").

         (b)      Registrant's Quarterly Report on Form 10-Q for the fiscal
                  quarter ended March 31, 1998 filed pursuant to Section 13(a)
                  of the Exchange Act.

         (c)      Registrant's Quarterly Report on Form 10-Q for the fiscal
                  quarter ended December 31, 1997 filed pursuant to Section 
                  13(a) of the Exchange Act.

         (d)      Registrant's Quarterly Report on Form 10-Q for the fiscal
                  quarter ended September 30, 1997 filed pursuant to Section 
                  13(a) of the Exchange Act.

         (e)      The description of the Registrant's Common Stock as set forth
                  in the Registration Statement filed by the Registrant on Form
                  8-A on March 29, 1989 (File No. 000-09992) pursuant to Section
                  12(g) of the Exchange Act and any amendments or reports
                  thereto filed with the Securities and Exchange Commission for
                  the purpose of updating such description including Amendment
                  No. 1 to Form 8-A filed September 25, 1995 and Amendment No. 2
                  to Form 8-A filed September 24, 1996.

         All documents subsequently filed by the Registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment to this registration statement which indicates that all
securities offered hereby have been sold or which deregisters all securities
remaining unsold, shall be deemed to be incorporated by reference in this
registration statement and to be a part hereof from the date of filing of such
documents.

ITEM 4.  DESCRIPTION OF SECURITIES.

         The class of securities to be offered is registered under Section 12 of
the Exchange Act.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

         Inapplicable.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Section 145(a) of the Delaware General Corporation Law (the "DGCL")
provides in relevant part that "[a] corporation may indemnify any person who was
or is a party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he is or was a director, officer, employee or agent of
the corporation, or is or was serving at the request of the corporation as a
director, officer, employee or agent of another corporation, partnership, joint
venture, trust or other enterprise, against expenses (including attorneys'
fees), judgments, fines and amounts paid in settlement actually and reasonably
incurred by him in connection with such action, suit or proceeding if he acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the corporation, and, with respect to any criminal action
or proceeding, had no reasonable cause to believe his conduct was unlawful."
With respect to derivative actions, Section 145(b) of the DGCL provides in
relevant part that "[a] corporation may indemnify any person who was or is a
party or is threatened to be made a party to any

                                      II-1

<PAGE>   3



threatened, pending or completed action or suit by or in the right of the
corporation to procure a judgment in its favor... [by reason of his service in
one of the capacities specified in the preceding sentence] against expenses
(including attorneys' fees) actually and reasonably incurred by him in
connection with the defense or settlement of such action or suit if he acted in
good faith and in a manner he reasonably believed to be in or not opposed to the
best interests of the corporation and except that no indemnification shall be
made in respect of any claim, issue or matter as to which such person shall have
been adjudged to be liable to the corporation unless and only to the extent that
the Court of Chancery or the court in which such action or suit was brought
shall determine upon application that, despite the adjudication of liability but
in view of all the circumstances of the case, such person is fairly and
reasonably entitled to indemnity for such expenses which the Court of Chancery
or such other court shall deem proper."

         The Company's Amended and Restated Certificate of Incorporation
provides that to the fullest extent permitted by the DGCL, no director of the
Company shall be personally liable to the Company or its stockholders for
monetary damages for breach of fiduciary duty as a director. The Amended and
Restated Certificate of Incorporation also provides that no amendment or repeal
of such provision shall apply to or have any effect on the right to
indemnification permitted thereunder with respect to claims arising from acts or
omissions occurring in whole or in part before the effective date of such
amendment or repeal whether asserted before or after such amendment or repeal.

         The Company's Bylaws provide that the Company shall indemnify to the
full extent permitted by the DGCL each of its directors, officers, employees and
other agents against expenses actually and reasonably incurred in connection
with any proceeding arising by reason of the fact that such person is or was an
agent of the Company.

         The Company has entered into indemnification agreements with its
directors and executive officers and intends to enter into indemnification
agreements with any new directors and executive officers in the future.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED

         Inapplicable.

ITEM 8.  EXHIBITS

         See Exhibit Index.

ITEM 9.  UNDERTAKINGS

         (a)      The undersigned registrant hereby undertakes:

                  (1) To file, during any period in which offers or sales are
being made, a post-effective amendment to this registration statement to include
any material information with respect to the plan of distribution not previously
disclosed in the registration statement or any material change to such
information in the registration statement.

                  (2) That, for the purpose of determining any liability under
the Securities Act of 1933, each such post-effective amendment shall be deemed
to be a new registration statement relating to the securities offered therein,
and the offering of such securities at that time shall be deemed to be the
initial bona fide offering thereof.

                  (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

                                      II-2

<PAGE>   4



         (b) The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

         (c) Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.


                                      II-3

<PAGE>   5


                                   SIGNATURES


         Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of San Jose, State of California, on August 7, 1998.


                           KLA-TENCOR CORPORATION

                           By: /s/ Lisa C. Berry
                               -------------------------------------------------
                               Lisa C. Berry, Vice President and General Counsel


                                    II-4

<PAGE>   6



                                POWER OF ATTORNEY

         KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Kenneth Levy and Lisa C. Berry, and each
of them, their true and lawful attorneys and agents, with full power of
substitution, each with power to act alone, to sign and execute on behalf of the
undersigned any amendment or amendments to this Registration Statement on Form
S-8 and to perform any acts necessary in order to file such amendments, and each
of the undersigned does hereby ratify and confirm all that said attorneys and
agents, or their or his or her substitutes, shall do or cause to be done by
virtue hereof. Pursuant to the requirements of the Securities Act of 1933, as
amended, this Registration Statement has been signed by the following persons in
the capacities and on the dates indicated.

<TABLE>

                      Signature                        Title                             Date
<S>                                        <C>                             
/s/ Kenneth Levy                           Chief Executive Officer and              August 7, 1998
----------------------------------         Director-(Principal-Executive
Kenneth Levy                               Officer)

/s/ Jon D. Tompkins                        Chairman of the Board and                August 7, 1998
----------------------------------         Director
Jon D. Tompkins

/s/ Kenneth L. Schroeder                   President, Chief Operating               August 7, 1998
----------------------------------         Officer and Director
Kenneth L. Schroeder

/s/ Robert J. Boehlke                      Executive Vice President                 August 7, 1998
----------------------------------         Administration and Finance, and
Robert J. Boehlke                          Chief Financial Officer (Principal
                                           Financial and Accounting
                                           Officer)

/s/ James W. Bagley                        Director                                 August 7, 1998
----------------------------------- 
James W. Bagley

/s/ Edward W. Barnholt                     Director                                 August 7, 1998
----------------------------------- 
Edward W. Barnholt

/s/ Leo J. Chamberlain                     Director                                 August 7, 1998
-----------------------------------
Leo J. Chamberlain

/s/ Richard J. Elkus, Jr.                  Director                                 August 7, 1998
-----------------------------------
Richard J. Elkus, Jr.

/s/ Dean O. Morton                         Director                                 August 7, 1998
-----------------------------------
Dean O. Morton

/s/ Yoshio Nishi                           Director                                 August 7, 1998
-----------------------------------
Yoshio Nishi

/s/ Samuel Rubinovitz                      Director                                 August 7, 1998
-----------------------------------
Samuel Rubinovitz

/s/ Dag Tellefsen                          Director                                 August 7, 1998
-----------------------------------
Dag Tellefsen

/s/ Lida Urbanek                           Director                                 August 7, 1998
-----------------------------------
Lida Urbanek

</TABLE>
                                      II-5

<PAGE>   7


                             KLA-TENCOR CORPORATION

                       REGISTRATION STATEMENT ON FORM S-8

                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>
Exhibit
Number                                 Description
-------        --------------------------------------------------------------
<S>            <C>
    4.1*       Certificate of Incorporation, as amended.

    4.2**      Bylaws of the Registrant, as amended.

    4.3***     Amended and Restated Rights Agreement dated as of August 30,
               1995 between the Registrant and The First National Bank of
               Boston, as Rights Agent.

    5.1        Opinion re: legality

   10.74+      Restated 1982 Stock Option Plan, as amended on November 18, 1996.

   23.1        Consent of Counsel (included in Exhibit 5.1)

   23.2        Consent of Independent Accountants

   24.1        Power of Attorney (see Page II-5)
---------------------------------------
</TABLE>
         *        Previously filed as Exhibit 3.1 to the Registrant's Quarterly
                  Report on Form 10-Q for the fiscal quarter ended March 31, 
                  1997 (filed on May 14, 1997, SEC File No. 000-09992).

         **       Previously filed as Exhibit 3.2 to the Registrant's Quarterly
                  Report on Form 10-Q for the fiscal quarter ended March 31, 
                  1997 (filed on May 14, 1997, SEC File No. 000-09992).

         ***      Incorporated by reference to Exhibit 1 of the Registrant's 
                  report on Form 8-A/A Amendment No. 1 to the Registration 
                  Statement on Form 8-A (filed September 24, 1996, Commission 
                  File No. 000-09992).

         +        Incorporated by reference to Exhibit 10.74 to the Registrant's
                  Registration Statement on Form S-8, dated March 7, 1997.
                  (Commission File No. 333-22941)

                                      II-6
[{"type": "S-8", "sequence": "1", "description": "FORM S-8 REGISTRATION STATEMENT", "secsgml_size_bytes": 19274}]
{"company-data": {"conformed-name": "KLA TENCOR CORP", "cik": "0000319201", "assigned-sic": "3827", "irs-number": "042564110", "state-of-incorporation": "DE", "fiscal-year-end": "0630"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-60887", "film-number": "98679279"}, "business-address": {"street1": "160 RIO ROBLES", "city": "SAN JOSE", "state": "CA", "zip": "95134", "phone": "4084344200"}, "mail-address": {"street1": "160 RIO ROBLES", "city": "SAN JOSE", "state": "CA", "zip": "95161-9055"}, "former-company": {"former-conformed-name": "KLA INSTRUMENTS CORP", "date-changed": "19920703"}}
1
          As filed with the Securities and Exchange Commission on August 7, 1998
                                                   Registration No. 333-________

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

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

                             KLA-TENCOR CORPORATION
             (Exact name of registrant as specified in its charter)
DELAWARE                                           04-2564110
(State of incorporation)                    (I.R.S. Employer Identification No.)
160 Rio Robles
                               San Jose, CA 95134
          (Address, including zip code, of principal executive offices)

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

                        RESTATED 1982 STOCK OPTION PLAN
                           (Full Titles of the Plans)

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

                                  LISA C. BERRY
                         VICE PRESIDENT, GENERAL COUNSEL
                             KLA-TENCOR CORPORATION
                                 160 Rio Robles
                               San Jose, CA 95134
                     (Name and address of agent for service)
                                 (408) 875-3000
          (Telephone number, including area code, of agent for service)

                                    Copy to:
                             JUDITH M. O'BRIEN, ESQ.
                        WILSON SONSINI GOODRICH & ROSATI
                            Professional Corporation
                               650 Page Mill Road
                        Palo Alto, California 94304-1050

================================================================================
                         CALCULATION OF REGISTRATION FEE
================================================================================
Proposed Maximum           Proposed Maximum
 Title of Securities to be     Amount to be              Offering Price Per         Aggregate offering        Amount of Registration
        Registered              Registered                   Share(1)                    Price(1)                      Fee
---------------------------  ----------------------  -------------------------  ---------------------------   ----------------------
Common Stock, $.001              2,618,837                  $28.8125                    $75,455,241                 $22,865
par value, to be issued
upon exercise of options
granted under the
Restated 1982 Stock
Option Plan
Total                            2,618,837                  $28.8125                    $75,455,241                  $22,865
-----                            ---------                  --------                    -----------                  -------
(1) The Proposed Maximum Offering Price Per Share was estimated in accordance
    with Rule 457(c) and Rule 457(h) under the Securities Act of 1933, as
    amended, (the "SECURITIES ACT") solely for the purpose of calculating the
    registration fee, based on the average between the high and low price of the
    Registrant's stock as reported in the Nasdaq National Market on August 3,
    1998.
2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         KLA-Tencor Corporation (the "REGISTRANT" or the "COMPANY") hereby
incorporates by reference in this registration statement the following
documents:

         (a)      The Registrant's Annual Report on Form 10-K for the fiscal
                  year ended June 30, 1997 (File No. 000-09992) pursuant to
                  Section 13(a) of the Securities Exchange Act of 1934, as
                  amended (the "Exchange Act").

         (b)      Registrant's Quarterly Report on Form 10-Q for the fiscal
                  quarter ended March 31, 1998 filed pursuant to Section 13(a)
                  of the Exchange Act.

         (c)      Registrant's Quarterly Report on Form 10-Q for the fiscal
                  quarter ended December 31, 1997 filed pursuant to Section 
                  13(a) of the Exchange Act.

         (d)      Registrant's Quarterly Report on Form 10-Q for the fiscal
                  quarter ended September 30, 1997 filed pursuant to Section 
                  13(a) of the Exchange Act.

         (e)      The description of the Registrant's Common Stock as set forth
                  in the Registration Statement filed by the Registrant on Form
                  8-A on March 29, 1989 (File No. 000-09992) pursuant to Section
                  12(g) of the Exchange Act and any amendments or reports
                  thereto filed with the Securities and Exchange Commission for
                  the purpose of updating such description including Amendment
                  No. 1 to Form 8-A filed September 25, 1995 and Amendment No. 2
                  to Form 8-A filed September 24, 1996.

         All documents subsequently filed by the Registrant pursuant to Sections
13(a), 13(c), 14 and 15(d) of the Exchange Act, prior to the filing of a
post-effective amendment to this registration statement which indicates that all
securities offered hereby have been sold or which deregisters all securities
remaining unsold, shall be deemed to be incorporated by reference in this
registration statement and to be a part hereof from the date of filing of such
documents.

ITEM 4.  DESCRIPTION OF SECURITIES.

         The class of securities to be offered is registered under Section 12 of
the Exchange Act.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

         Inapplicable.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Section 145(a) of the Delaware General Corporation Law (the "DGCL")
provides in relevant part that "[a] corporation may indemnify any person who was
or is a party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding, whether civil, criminal, administrative or
investigative (other than an action by or in the right of the corporation) by
reason of the fact that he is or was a director, officer, employee or agent of
the corporation, or is or was serving at the request of the corporation as a
director, officer, employee or agent of another corporation, partnership, joint
venture, trust or other enterprise, against expenses (including attorneys'
fees), judgments, fines and amounts paid in settlement actually and reasonably
incurred by him in connection with such action, suit or proceeding if he acted
in good faith and in a manner he reasonably believed to be in or not opposed to
the best interests of the corporation, and, with respect to any criminal action
or proceeding, had no reasonable cause to believe his conduct was unlawful."
With respect to derivative actions, Section 145(b) of the DGCL provides in
relevant part that "[a] corporation may indemnify any person who was or is a
party or is threatened to be made a party to any

                                      II-1
3

threatened, pending or completed action or suit by or in the right of the
corporation to procure a judgment in its favor... [by reason of his service in
one of the capacities specified in the preceding sentence] against expenses
(including attorneys' fees) actually and reasonably incurred by him in
connection with the defense or settlement of such action or suit if he acted in
good faith and in a manner he reasonably believed to be in or not opposed to the
best interests of the corporation and except that no indemnification shall be
made in respect of any claim, issue or matter as to which such person shall have
been adjudged to be liable to the corporation unless and only to the extent that
the Court of Chancery or the court in which such action or suit was brought
shall determine upon application that, despite the adjudication of liability but
in view of all the circumstances of the case, such person is fairly and
reasonably entitled to indemnity for such expenses which the Court of Chancery
or such other court shall deem proper."

         The Company's Amended and Restated Certificate of Incorporation
provides that to the fullest extent permitted by the DGCL, no director of the
Company shall be personally liable to the Company or its stockholders for
monetary damages for breach of fiduciary duty as a director. The Amended and
Restated Certificate of Incorporation also provides that no amendment or repeal
of such provision shall apply to or have any effect on the right to
indemnification permitted thereunder with respect to claims arising from acts or
omissions occurring in whole or in part before the effective date of such
amendment or repeal whether asserted before or after such amendment or repeal.

         The Company's Bylaws provide that the Company shall indemnify to the
full extent permitted by the DGCL each of its directors, officers, employees and
other agents against expenses actually and reasonably incurred in connection
with any proceeding arising by reason of the fact that such person is or was an
agent of the Company.

         The Company has entered into indemnification agreements with its
directors and executive officers and intends to enter into indemnification
agreements with any new directors and executive officers in the future.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED

         Inapplicable.

ITEM 8.  EXHIBITS

         See Exhibit Index.

ITEM 9.  UNDERTAKINGS

         (a)      The undersigned registrant hereby undertakes:

                  (1) To file, during any period in which offers or sales are
being made, a post-effective amendment to this registration statement to include
any material information with respect to the plan of distribution not previously
disclosed in the registration statement or any material change to such
information in the registration statement.

                  (2) That, for the purpose of determining any liability under
the Securities Act of 1933, each such post-effective amendment shall be deemed
to be a new registration statement relating to the securities offered therein,
and the offering of such securities at that time shall be deemed to be the
initial bona fide offering thereof.

                  (3) To remove from registration by means of a post-effective
amendment any of the securities being registered which remain unsold at the
termination of the offering.

                                      II-2
4

         (b) The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
registration statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

         (c) Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Act and will
be governed by the final adjudication of such issue.

                                      II-3
5

                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of San Jose, State of California, on August 7, 1998.

                           KLA-TENCOR CORPORATION

                           By: /s/ Lisa C. Berry
                               -------------------------------------------------
                               Lisa C. Berry, Vice President and General Counsel

                                    II-4
6

                                POWER OF ATTORNEY

         KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Kenneth Levy and Lisa C. Berry, and each
of them, their true and lawful attorneys and agents, with full power of
substitution, each with power to act alone, to sign and execute on behalf of the
undersigned any amendment or amendments to this Registration Statement on Form
S-8 and to perform any acts necessary in order to file such amendments, and each
of the undersigned does hereby ratify and confirm all that said attorneys and
agents, or their or his or her substitutes, shall do or cause to be done by
virtue hereof. Pursuant to the requirements of the Securities Act of 1933, as
amended, this Registration Statement has been signed by the following persons in
the capacities and on the dates indicated.

                      Signature                        Title                             Date
/s/ Kenneth Levy                           Chief Executive Officer and              August 7, 1998
----------------------------------         Director-(Principal-Executive
Kenneth Levy                               Officer)

/s/ Jon D. Tompkins                        Chairman of the Board and                August 7, 1998
----------------------------------         Director
Jon D. Tompkins

/s/ Kenneth L. Schroeder                   President, Chief Operating               August 7, 1998
----------------------------------         Officer and Director
Kenneth L. Schroeder

/s/ Robert J. Boehlke                      Executive Vice President                 August 7, 1998
----------------------------------         Administration and Finance, and
Robert J. Boehlke                          Chief Financial Officer (Principal
                                           Financial and Accounting
                                           Officer)

/s/ James W. Bagley                        Director                                 August 7, 1998
----------------------------------- 
James W. Bagley

/s/ Edward W. Barnholt                     Director                                 August 7, 1998
----------------------------------- 
Edward W. Barnholt

/s/ Leo J. Chamberlain                     Director                                 August 7, 1998
-----------------------------------
Leo J. Chamberlain

/s/ Richard J. Elkus, Jr.                  Director                                 August 7, 1998
-----------------------------------
Richard J. Elkus, Jr.

/s/ Dean O. Morton                         Director                                 August 7, 1998
-----------------------------------
Dean O. Morton

/s/ Yoshio Nishi                           Director                                 August 7, 1998
-----------------------------------
Yoshio Nishi

/s/ Samuel Rubinovitz                      Director                                 August 7, 1998
-----------------------------------
Samuel Rubinovitz

/s/ Dag Tellefsen                          Director                                 August 7, 1998
-----------------------------------
Dag Tellefsen

/s/ Lida Urbanek                           Director                                 August 7, 1998
-----------------------------------
Lida Urbanek
II-5
7

                             KLA-TENCOR CORPORATION

                       REGISTRATION STATEMENT ON FORM S-8

                                INDEX TO EXHIBITS
Exhibit
Number                                 Description
-------        --------------------------------------------------------------
4.1*       Certificate of Incorporation, as amended.

    4.2**      Bylaws of the Registrant, as amended.

    4.3***     Amended and Restated Rights Agreement dated as of August 30,
               1995 between the Registrant and The First National Bank of
               Boston, as Rights Agent.

    5.1        Opinion re: legality

   10.74+      Restated 1982 Stock Option Plan, as amended on November 18, 1996.

   23.1        Consent of Counsel (included in Exhibit 5.1)

   23.2        Consent of Independent Accountants

   24.1        Power of Attorney (see Page II-5)
---------------------------------------
*        Previously filed as Exhibit 3.1 to the Registrant's Quarterly
                  Report on Form 10-Q for the fiscal quarter ended March 31, 
                  1997 (filed on May 14, 1997, SEC File No. 000-09992).

         **       Previously filed as Exhibit 3.2 to the Registrant's Quarterly
                  Report on Form 10-Q for the fiscal quarter ended March 31, 
                  1997 (filed on May 14, 1997, SEC File No. 000-09992).

         ***      Incorporated by reference to Exhibit 1 of the Registrant's 
                  report on Form 8-A/A Amendment No. 1 to the Registration 
                  Statement on Form 8-A (filed September 24, 1996, Commission 
                  File No. 000-09992).

         +        Incorporated by reference to Exhibit 10.74 to the Registrant's
                  Registration Statement on Form S-8, dated March 7, 1997.
                  (Commission File No. 333-22941)

                                      II-6