<PAGE>   1

    As filed with the Securities and Exchange Commission on December 4, 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, California 95134
          (Address, including zip code, of principal executive offices)

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

                        1998 OUTSIDE DIRECTOR OPTION PLAN
                           (Full Titles of the Plans)

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

                                  LISA C. BERRY
                         VICE PRESIDENT, GENERAL COUNSEL
                             KLA-TENCOR CORPORATION
                                 160 Rio Robles
                           San Jose, California 95134
                     (Name and address of agent for service)
                                 (408) 875-4200
          (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


<TABLE>
<CAPTION>
======================================================================================================================
                                            CALCULATION OF REGISTRATION FEE
======================================================================================================================
                                    Proposed Maximum    Proposed Maximum
Title of Securities                   Amount to be       Offering Price           Aggregate              Amount of
to be Registered                       Registered         Per Share(1)        Offering Price(1)       Registration Fee
----------------------------------------------------------------------------------------------------------------------
<S>                                    <C>                  <C>                <C>                       <C>
Common Stock,
$.001 par value

Newly reserved under 1998  
Outside Director Option Plan           1,000,000             $35.50            $35,500,000.00            $10,757.58
</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 System on
     November 30, 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)  Registrant's Annual Report on Form 10-K for the fiscal year ended June
          30, 1998 and Amendment No. 1 to Form 10-K (File No. 000-09992),
          pursuant to Section 13(a) of the Securities Exchange Act of 1934, as
          amended (the "EXCHANGE ACT");

     (b)  Registrant's definitive proxy statement dated September 30, 1998 (File
          No. 000-09992), filed in connection with the November 17, 1998 Annual
          Meeting of Stockholders of the Company;

     (c)  Registrant's Quarterly Report on Form 10-Q for the fiscal quarter
          ended September 30, 1998 (File No. 000-09992), filed pursuant to
          Section 13(a) of the Exchange Act;

     (d)  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.

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.

     Not applicable.

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


                                      II-1

<PAGE>   3

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 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

     Not applicable.

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 December 4, 1998.
KLA-TENCOR CORPORATION

                                        By: /s/ Kenneth Levy
                                           -------------------------------------
                                           Kenneth Levy, Chief Executive Officer


                                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>
<CAPTION>
          Signature                            Title                             Date
          ---------                            -----                             ----
<S>                               <C>                                       <C>
/s/ Kenneth Levy                  Chief Executive Officer and Director      December 4, 1998
-------------------------------   (Principal-Executive-Officer)
Kenneth Levy

/s/ Jon D. Tompkins               Chairman of the Board and Director        December 4, 1998
-------------------------------   
Jon D. Tompkins

/s/ Kenneth L. Schroeder          President, Chief Operating Officer        December 4, 1998
-------------------------------   and Director
Kenneth L. Schroeder

/s/ Robert J. Boehlke             Executive Vice President and Chief        December 4, 1998
-------------------------------   Financial Officer (Principal
Robert J. Boehlke                 Financial and Accounting Officer)

/s/ James W. Bagley               Director                                  December 4, 1998
-------------------------------
James W. Bagley

 /s/ Edward W. Barnholt           Director                                  December 4, 1998
-------------------------------
Edward W. Barnholt

/s/ Leo J. Chamberlain            Director                                  December 4, 1998
-------------------------------
Leo J. Chamberlain

/s/ Richard J. Elkus, Jr.         Director                                  December 4, 1998
-------------------------------
Richard J. Elkus, Jr.

/s/ Dean O. Morton                Director                                  December 4, 1998
-------------------------------
Dean O. Morton

/s/ Samuel Rubinovitz             Director                                  December 4, 1998
-------------------------------
Samuel Rubinovitz

/s/ Dag Tellefsen                 Director                                  December 4, 1998
-------------------------------
Dag Tellefsen

/s/ Lida Urbanek                  Director                                  December 4, 1998
-------------------------------
Lida Urbanek
</TABLE>


                                      II-4

<PAGE>   6

                             KLA-TENCOR CORPORATION

                       REGISTRATION STATEMENT ON FORM S-8

                                INDEX TO EXHIBITS


<TABLE>
<CAPTION>
Exhibit
Number                              Description
-------             --------------------------------------------
<S>                 <C>
   5.1              Opinion re: legality

  10.1              1998 Outside Director Option Plan

  23.1              Consent of Counsel (included in Exhibit 5.1)

  23.2              Consent of Independent Accountants

  24.1              Power of Attorney (see Page II-4)
</TABLE>
------------


                                      II-5
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 16617}]
{"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": "333-68423", "film-number": "98764431"}, "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 December 4, 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, California 95134
          (Address, including zip code, of principal executive offices)

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

                        1998 OUTSIDE DIRECTOR OPTION PLAN
                           (Full Titles of the Plans)

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

                                  LISA C. BERRY
                         VICE PRESIDENT, GENERAL COUNSEL
                             KLA-TENCOR CORPORATION
                                 160 Rio Robles
                           San Jose, California 95134
                     (Name and address of agent for service)
                                 (408) 875-4200
          (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
======================================================================================================================
                                            CALCULATION OF REGISTRATION FEE
======================================================================================================================
                                    Proposed Maximum    Proposed Maximum
Title of Securities                   Amount to be       Offering Price           Aggregate              Amount of
to be Registered                       Registered         Per Share(1)        Offering Price(1)       Registration Fee
----------------------------------------------------------------------------------------------------------------------
Common Stock,
$.001 par value

Newly reserved under 1998  
Outside Director Option Plan           1,000,000             $35.50            $35,500,000.00            $10,757.58
--------
           
(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 System on
     November 30, 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)  Registrant's Annual Report on Form 10-K for the fiscal year ended June
          30, 1998 and Amendment No. 1 to Form 10-K (File No. 000-09992),
          pursuant to Section 13(a) of the Securities Exchange Act of 1934, as
          amended (the "EXCHANGE ACT");

     (b)  Registrant's definitive proxy statement dated September 30, 1998 (File
          No. 000-09992), filed in connection with the November 17, 1998 Annual
          Meeting of Stockholders of the Company;

     (c)  Registrant's Quarterly Report on Form 10-Q for the fiscal quarter
          ended September 30, 1998 (File No. 000-09992), filed pursuant to
          Section 13(a) of the Exchange Act;

     (d)  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.

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.

     Not applicable.

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

                                      II-1
3

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 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

     Not applicable.

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 December 4, 1998.
KLA-TENCOR CORPORATION

                                        By: /s/ Kenneth Levy
                                           -------------------------------------
                                           Kenneth Levy, Chief Executive Officer

                                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 Director      December 4, 1998
-------------------------------   (Principal-Executive-Officer)
Kenneth Levy

/s/ Jon D. Tompkins               Chairman of the Board and Director        December 4, 1998
-------------------------------   
Jon D. Tompkins

/s/ Kenneth L. Schroeder          President, Chief Operating Officer        December 4, 1998
-------------------------------   and Director
Kenneth L. Schroeder

/s/ Robert J. Boehlke             Executive Vice President and Chief        December 4, 1998
-------------------------------   Financial Officer (Principal
Robert J. Boehlke                 Financial and Accounting Officer)

/s/ James W. Bagley               Director                                  December 4, 1998
-------------------------------
James W. Bagley

 /s/ Edward W. Barnholt           Director                                  December 4, 1998
-------------------------------
Edward W. Barnholt

/s/ Leo J. Chamberlain            Director                                  December 4, 1998
-------------------------------
Leo J. Chamberlain

/s/ Richard J. Elkus, Jr.         Director                                  December 4, 1998
-------------------------------
Richard J. Elkus, Jr.

/s/ Dean O. Morton                Director                                  December 4, 1998
-------------------------------
Dean O. Morton

/s/ Samuel Rubinovitz             Director                                  December 4, 1998
-------------------------------
Samuel Rubinovitz

/s/ Dag Tellefsen                 Director                                  December 4, 1998
-------------------------------
Dag Tellefsen

/s/ Lida Urbanek                  Director                                  December 4, 1998
-------------------------------
Lida Urbanek
II-4
6

                             KLA-TENCOR CORPORATION

                       REGISTRATION STATEMENT ON FORM S-8

                                INDEX TO EXHIBITS
Exhibit
Number                              Description
-------             --------------------------------------------
5.1              Opinion re: legality

  10.1              1998 Outside Director Option Plan

  23.1              Consent of Counsel (included in Exhibit 5.1)

  23.2              Consent of Independent Accountants

  24.1              Power of Attorney (see Page II-4)
------------

                                      II-5