<PAGE>
       As filed with the Securities and Exchange Commission on December 26, 2001

                                                      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
             AMENDED AND RESTATED 1997 EMPLOYEE STOCK PURCHASE PLAN
                           (Full Titles of the Plans)

                                STUART J. NICHOLS
                         VICE PRESIDENT, GENERAL COUNSEL
                             KLA-TENCOR CORPORATION
                                 160 Rio Robles
                               San Jose, CA 95134
                     (Name and address of agent for service)

                                 (408) 875-4200
          (Telephone number, including area code, of agent for service)


                                    Copy to:

                             MARK L. REINSTRA, ESQ.
                              BRET M. DIMARCO, ESQ.
                        WILSON SONSINI GOODRICH & ROSATI
                            Professional Corporation
                               650 Page Mill Road
                        Palo Alto, California 94304-1050
                                 (650) 493-9300

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

<PAGE>

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
                                                         Proposed Maximum    Proposed Maximum      Amount of
                                          Amount to be    Offering Price    Aggregate Offering   Registration
Title of Securities to be Registered      Registered(1)      Per Share            Price              Fee(4)
-------------------------------------------------------------------------------------------------------------
<S>                                      <C>             <C>                 <C>                  <C>
Common Stock, $.001 par value, to be       5,610,752          $49.86(2)      $279,752,094.72       $66,860.75
issued under the Restated 1982 Stock
Option Plan

Common Stock, $.001 par value, to be       2,000,000          $42.38(3)       $84,762,000.00       $20,258.12
issued under the Amended and
Restated 1997 Employee Stock
Purchase Plan

                               Total:      7,610,752                         $364,514,094.72       $87,118.87
</TABLE>

----------

(1)  Amount of securities to be registered computed in accordance with Rule
     457(h) of the Securities Act of 1933, as amended, (the "Securities Act") as
     the maximum number of the Registrant's Common Stock issuable under the
     plans covered by this Registration Statement. Pursuant to Rule 416(a) of
     the Securities Act, this Registration Statement shall also cover any
     additional shares of the Registrant's Common Stock that become issuable
     under the plans covered by this Registration Statement by reason of any
     stock split, stock dividend, recapitalization or other similar transaction
     effected without the Registrant's receipt of consideration that results in
     an increase in the number of the Registrant's outstanding shares of Common
     Stock.

(2)  Estimated in accordance with Rule 457(c) of the Securities Act solely for
     the purpose of calculating the registration fee based on the average of the
     high and low prices per share of the Common Stock as reported on The Nasdaq
     National Market on December 24, 2001.

(3)  Estimated in accordance with Rule 457(c) of the Securities Act solely for
     the purpose of calculating the registration fee based on 85% of the average
     of the high and low prices per share of the Common Stock as reported on The
     Nasdaq National Market on December 24, 2001.

(4)  Amount of registration fee was calculated pursuant to Section 6(b) of the
     Securities Act, which provides that the fee shall be $239 per $1,000,000 of
     the proposed maximum aggregate offering price of the securities proposed to
     be registered.

<PAGE>

                                     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, 2001 (File No. 000-09992) pursuant to Section 13(a) of the
          Securities Exchange Act of 1934, as amended (the "EXCHANGE ACT");

     (b)  All other reports filed by the Registrant pursuant to Section 13(a) or
          15(d) of the Exchange Act since the end of the fiscal year covered by
          the Annual Report referred to in (a) above;

     (c)  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; and

     (d)  All other descriptions of the Registrant's Common Stock contained in a
          registration statement filed under the Exchange Act, including any
          amendment or report filed for the purpose of updating such
          description.

     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.

     Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not applicable.

                                      II-1

<PAGE>

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 shall have power to 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 the person 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 the person in connection with
such action, suit or proceeding if the person acted in good faith and in a
manner the person 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 the person's conduct was
unlawful." With respect to derivative actions, Section 145(b) of the DGCL
provides in relevant part that "[a] corporation shall have power to 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 the person's
service in one of the capacities specified in the preceding sentence] against
expenses (including attorneys' fees) actually and reasonably incurred by the
person in connection with the defense or settlement of such action or suit if
the person acted in good faith and in a manner 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 Registrant's Amended and Restated Certificate of Incorporation provides
that to the fullest extent permitted by the DGCL, no director of the Registrant
shall be personally liable to the Registrant 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 Registrant's Bylaws provide that the Registrant shall indemnify to the
fullest 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 Registrant.

     The Registrant 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.

                                      II-2

<PAGE>

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:

               (i)    To include any prospectus required by Section 10(a)(3) of
                      the Securities Act of 1933;

               (ii)   To reflect in the prospectus any facts or events arising
                      after the effective date of the Registration Statement (or
                      the most recent post-effective amendment thereof) which,
                      individually or in the aggregate, represent a fundamental
                      changes in the information set forth in the Registration
                      Statement.

               (iii)  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.

Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed by the Registrant pursuant to
Section 13 or Section 15(d) of the Securities Exchange Act 1934 that are
incorporated by reference 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.

     (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>

                                   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 26, 2001.

                                        KLA-TENCOR CORPORATION

                                        By: /s/   STUART J. NICHOLS
                                            ------------------------------------
                                            Stuart J. Nichols, Vice President,
                                            General Counsel

                                      II-4

<PAGE>

                                POWER OF ATTORNEY

     KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Stuart J. Nichols, their true and lawful
attorney and agent, with full power of substitution, with the 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 attorney and agent, or his substitute,
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            Chairman of the Board and      December 26, 2001
---------------------------  Director
Kenneth Levy


/s/  KENNETH L. SCHROEDER    President, Chief Executive     December 26, 2001
---------------------------  Officer and Director
Kenneth L. Schroeder         (Principal Executive
                             Officer)


/s/  JOHN H. KISPERT         Chief Financial Officer        December 26, 2001
---------------------------  (Principal Financial and
John H. Kispert              Accounting Officer)



/s/  EDWARD W. BARNHOLT      Director                       December 26, 2001
---------------------------
Edward W. Barnholt


/s/  H. RAYMOND BINGHAM      Director                       December 26, 2001
---------------------------
H. Raymond Bingham


/s/  ROBERT T. BOND          Director                       December 26, 2001
---------------------------
Robert T. Bond


/s/  RICHARD J. ELKUS, JR.   Director                       December 26, 2001
---------------------------
Richard J. Elkus, Jr.


/s/  DEAN O. MORTON          Director                       December 26, 2001
---------------------------
Dean O. Morton


/s/  JON D. TOMPKINS         Director                       December 26, 2001
---------------------------
Jon D. Tompkins


/s/  LIDA URBANEK            Director                       December 26, 2001
---------------------------
Lida Urbanek
</TABLE>

                                      II-5

<PAGE>

                             KLA-TENCOR CORPORATION

                       REGISTRATION STATEMENT ON FORM S-8


                                INDEX TO EXHIBITS

<TABLE>
<CAPTION>
Exhibit
Number                                  Description
-------                                 -----------
<S>          <C>
  4.1(1)     Amended and Restated Certificate of Incorporation, as amended.

  4.2(2)     Certificate of Amendment of Amended and Restated Certificate of
             Incorporation.

  4.3(3)     Bylaws of the Registrant, as amended.

  4.4(4)     Amended and Restated Rights Agreement dated as of April 25, 1996,
             between the Registrant and First National Bank of Boston, as Rights
             Agent. This agreement includes the Form of Right Certificate as
             Exhibit A and the Summary of Terms of Rights as Exhibit B thereto.

  5.1        Opinion re legality

 10.1        Amended and Restated 1997 Employee Stock Purchase Plan

 10.2(5)     Restated 1982 Stock Option Plan

 23.1        Consent of Independent Accountants

 23.2        Consent of Counsel (included in Exhibit 5.1)

 24.1        Power of Attorney (see Page II-5)
</TABLE>

----------

(1)  Incorporated by reference to Exhibit 3.1 to the Registrant's Quarterly
     Report on Form 10-Q for the quarter ended March 31, 1997 (Commission File
     No. 000-09992).

(2)  Incorporated by reference to Exhibit 3.1 to the Registrant's Quarterly
     Report on Form 10-Q, for the quarter ended December 31, 2000 (Commission
     File No. 000-09992).

(3)  Incorporated by reference to Exhibit 3.2 to the Registrant's Registration
     Statement on Form S-8, filed December 4, 1998 (Commission File No.
     333-68415).

(4)  Incorporated by reference to Exhibit 1 of the Registrant's report on Form
     8-A12G/A Amendment No. 2 to the Registration Statement on Form 8-A (filed
     September 24, 1996, Commission File No. 000-09992).

(5)  Incorporated by reference to Exhibit 10.74 to the Registrant's Registration
     Statement on Form S-8, filed March 7, 1997. (Commission File No.
     333-22941).
[{"type": "S-8", "sequence": "1", "filename": "f78041s-8.txt", "description": "FORM S-8 PERIOD ENDING DECEMBER 26, 2001", "secsgml_size_bytes": 20405}]
{"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": "333-75944", "film-number": "1822503"}, "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"}}
As filed with the Securities and Exchange Commission on December 26, 2001

                                                      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
             AMENDED AND RESTATED 1997 EMPLOYEE STOCK PURCHASE PLAN
                           (Full Titles of the Plans)

                                STUART J. NICHOLS
                         VICE PRESIDENT, GENERAL COUNSEL
                             KLA-TENCOR CORPORATION
                                 160 Rio Robles
                               San Jose, CA 95134
                     (Name and address of agent for service)

                                 (408) 875-4200
          (Telephone number, including area code, of agent for service)

                                    Copy to:

                             MARK L. REINSTRA, ESQ.
                              BRET M. DIMARCO, ESQ.
                        WILSON SONSINI GOODRICH & ROSATI
                            Professional Corporation
                               650 Page Mill Road
                        Palo Alto, California 94304-1050
                                 (650) 493-9300

--------------------------------------------------------------------------------
CALCULATION OF REGISTRATION FEE
Proposed Maximum    Proposed Maximum      Amount of
                                          Amount to be    Offering Price    Aggregate Offering   Registration
Title of Securities to be Registered      Registered(1)      Per Share            Price              Fee(4)
-------------------------------------------------------------------------------------------------------------
Common Stock, $.001 par value, to be       5,610,752          $49.86(2)      $279,752,094.72       $66,860.75
issued under the Restated 1982 Stock
Option Plan

Common Stock, $.001 par value, to be       2,000,000          $42.38(3)       $84,762,000.00       $20,258.12
issued under the Amended and
Restated 1997 Employee Stock
Purchase Plan

                               Total:      7,610,752                         $364,514,094.72       $87,118.87
----------

(1)  Amount of securities to be registered computed in accordance with Rule
     457(h) of the Securities Act of 1933, as amended, (the "Securities Act") as
     the maximum number of the Registrant's Common Stock issuable under the
     plans covered by this Registration Statement. Pursuant to Rule 416(a) of
     the Securities Act, this Registration Statement shall also cover any
     additional shares of the Registrant's Common Stock that become issuable
     under the plans covered by this Registration Statement by reason of any
     stock split, stock dividend, recapitalization or other similar transaction
     effected without the Registrant's receipt of consideration that results in
     an increase in the number of the Registrant's outstanding shares of Common
     Stock.

(2)  Estimated in accordance with Rule 457(c) of the Securities Act solely for
     the purpose of calculating the registration fee based on the average of the
     high and low prices per share of the Common Stock as reported on The Nasdaq
     National Market on December 24, 2001.

(3)  Estimated in accordance with Rule 457(c) of the Securities Act solely for
     the purpose of calculating the registration fee based on 85% of the average
     of the high and low prices per share of the Common Stock as reported on The
     Nasdaq National Market on December 24, 2001.

(4)  Amount of registration fee was calculated pursuant to Section 6(b) of the
     Securities Act, which provides that the fee shall be $239 per $1,000,000 of
     the proposed maximum aggregate offering price of the securities proposed to
     be registered.
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, 2001 (File No. 000-09992) pursuant to Section 13(a) of the
          Securities Exchange Act of 1934, as amended (the "EXCHANGE ACT");

     (b)  All other reports filed by the Registrant pursuant to Section 13(a) or
          15(d) of the Exchange Act since the end of the fiscal year covered by
          the Annual Report referred to in (a) above;

     (c)  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; and

     (d)  All other descriptions of the Registrant's Common Stock contained in a
          registration statement filed under the Exchange Act, including any
          amendment or report filed for the purpose of updating such
          description.

     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.

     Not applicable.

ITEM 5. INTERESTS OF NAMED EXPERTS AND COUNSEL.

     Not applicable.

                                      II-1
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 shall have power to 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 the person 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 the person in connection with
such action, suit or proceeding if the person acted in good faith and in a
manner the person 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 the person's conduct was
unlawful." With respect to derivative actions, Section 145(b) of the DGCL
provides in relevant part that "[a] corporation shall have power to 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 the person's
service in one of the capacities specified in the preceding sentence] against
expenses (including attorneys' fees) actually and reasonably incurred by the
person in connection with the defense or settlement of such action or suit if
the person acted in good faith and in a manner 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 Registrant's Amended and Restated Certificate of Incorporation provides
that to the fullest extent permitted by the DGCL, no director of the Registrant
shall be personally liable to the Registrant 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 Registrant's Bylaws provide that the Registrant shall indemnify to the
fullest 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 Registrant.

     The Registrant 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.

                                      II-2
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:

               (i)    To include any prospectus required by Section 10(a)(3) of
                      the Securities Act of 1933;

               (ii)   To reflect in the prospectus any facts or events arising
                      after the effective date of the Registration Statement (or
                      the most recent post-effective amendment thereof) which,
                      individually or in the aggregate, represent a fundamental
                      changes in the information set forth in the Registration
                      Statement.

               (iii)  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.

Provided, however, that paragraphs (a)(1)(i) and (a)(1)(ii) do not apply if the
information required to be included in a post-effective amendment by those
paragraphs is contained in periodic reports filed by the Registrant pursuant to
Section 13 or Section 15(d) of the Securities Exchange Act 1934 that are
incorporated by reference 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.

     (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
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 26, 2001.

                                        KLA-TENCOR CORPORATION

                                        By: /s/   STUART J. NICHOLS
                                            ------------------------------------
                                            Stuart J. Nichols, Vice President,
                                            General Counsel

                                      II-4
POWER OF ATTORNEY

     KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Stuart J. Nichols, their true and lawful
attorney and agent, with full power of substitution, with the 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 attorney and agent, or his substitute,
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            Chairman of the Board and      December 26, 2001
---------------------------  Director
Kenneth Levy

/s/  KENNETH L. SCHROEDER    President, Chief Executive     December 26, 2001
---------------------------  Officer and Director
Kenneth L. Schroeder         (Principal Executive
                             Officer)

/s/  JOHN H. KISPERT         Chief Financial Officer        December 26, 2001
---------------------------  (Principal Financial and
John H. Kispert              Accounting Officer)

/s/  EDWARD W. BARNHOLT      Director                       December 26, 2001
---------------------------
Edward W. Barnholt

/s/  H. RAYMOND BINGHAM      Director                       December 26, 2001
---------------------------
H. Raymond Bingham

/s/  ROBERT T. BOND          Director                       December 26, 2001
---------------------------
Robert T. Bond

/s/  RICHARD J. ELKUS, JR.   Director                       December 26, 2001
---------------------------
Richard J. Elkus, Jr.

/s/  DEAN O. MORTON          Director                       December 26, 2001
---------------------------
Dean O. Morton

/s/  JON D. TOMPKINS         Director                       December 26, 2001
---------------------------
Jon D. Tompkins

/s/  LIDA URBANEK            Director                       December 26, 2001
---------------------------
Lida Urbanek
II-5
KLA-TENCOR CORPORATION

                       REGISTRATION STATEMENT ON FORM S-8

                                INDEX TO EXHIBITS
Exhibit
Number                                  Description
-------                                 -----------
4.1(1)     Amended and Restated Certificate of Incorporation, as amended.

  4.2(2)     Certificate of Amendment of Amended and Restated Certificate of
             Incorporation.

  4.3(3)     Bylaws of the Registrant, as amended.

  4.4(4)     Amended and Restated Rights Agreement dated as of April 25, 1996,
             between the Registrant and First National Bank of Boston, as Rights
             Agent. This agreement includes the Form of Right Certificate as
             Exhibit A and the Summary of Terms of Rights as Exhibit B thereto.

  5.1        Opinion re legality

 10.1        Amended and Restated 1997 Employee Stock Purchase Plan

 10.2(5)     Restated 1982 Stock Option Plan

 23.1        Consent of Independent Accountants

 23.2        Consent of Counsel (included in Exhibit 5.1)

 24.1        Power of Attorney (see Page II-5)
----------

(1)  Incorporated by reference to Exhibit 3.1 to the Registrant's Quarterly
     Report on Form 10-Q for the quarter ended March 31, 1997 (Commission File
     No. 000-09992).

(2)  Incorporated by reference to Exhibit 3.1 to the Registrant's Quarterly
     Report on Form 10-Q, for the quarter ended December 31, 2000 (Commission
     File No. 000-09992).

(3)  Incorporated by reference to Exhibit 3.2 to the Registrant's Registration
     Statement on Form S-8, filed December 4, 1998 (Commission File No.
     333-68415).

(4)  Incorporated by reference to Exhibit 1 of the Registrant's report on Form
     8-A12G/A Amendment No. 2 to the Registration Statement on Form 8-A (filed
     September 24, 1996, Commission File No. 000-09992).

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