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                                  UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                   FORM 10-K/A

(MARK ONE)

[X]     ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE
        ACT OF 1934

        FOR THE FISCAL YEAR ENDED JANUARY 2, 2000

OR

[ ]     TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES
        EXCHANGE ACT OF 1934

        For the transition period from                 to

                         COMMISSION FILE NUMBER 0-16852

                               KOMAG, INCORPORATED
             (Exact name of Registrant as specified in its charter)

<TABLE>
<S>                                               <C>
             DELAWARE                                    94-2914864
(STATE OR OTHER JURISDICTION OF                       (I.R.S. EMPLOYER
 INCORPORATION OR ORGANIZATION)                    IDENTIFICATION NUMBER)
</TABLE>

               1710 AUTOMATION PARKWAY, SAN JOSE, CALIFORNIA 95131
          (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES, INCLUDING ZIP CODE)

         REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE: (408) 576-2000

Securities registered pursuant to Section 12(b) of the Act:

<TABLE>
<S>                                            <C>
                                                Name of each exchange
       Title of each class                       on which registered
       -------------------                       -------------------
              NONE                                      NONE
</TABLE>

Securities registered pursuant to Section 12(g) of the Act:

                          COMMON STOCK, $0.01 PAR VALUE

Indicate by check mark whether the Registrant (1) has filed all reports required
to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during
the preceding 12 months (or for such shorter period that the registrant was
required to file such reports), and (2) has been subject to such filing
requirements for the past 90 days. Yes  X   No
                                       ---    ---

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of the registrant's knowledge, in definitive proxy or information
statements incorporated by reference in Part III of this form 10-K/A or any
amendment of this Form 10-K/A. [ X ]

                            [COVER PAGE 1 OF 2 PAGES]


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     The aggregate market value of voting stock held by non-affiliates of the
Registrant as of September 26, 2000 was approximately $231,712,604.06 based upon
the closing sale price for shares of the Registrant's Common Stock as reported
by the Nasdaq National Market for the last trading date prior to that date).
Shares of Common Stock held by each officer, director and holder of 5% or more
of the outstanding Common Stock have been excluded in that such persons may be
deemed to be affiliates. This determination of affiliate status is not
necessarily a conclusive determination for other purposes.

     On September 26, 2000, approximately 66,800,030 shares of the Registrant's
Common Stock, $0.01 par value, were outstanding.

                       DOCUMENTS INCORPORATED BY REFERENCE

     Portions of the following document are incorporated by reference into this
Report on Form 10-K/A:

     Komag, Incorporated Proxy Statement for the Annual Meeting of Stockholders
held on May 10, 2000.


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                                     PART IV

ITEM 14.  EXHIBITS, FINANCIAL STATEMENT SCHEDULES AND REPORTS ON FORM 8-K.

     ALL FINANCIAL STATEMENTS, SCHEDULES AND EXHIBITS REQUIRED UNDER ITEM 14
WHICH ARE NOT PRESENTED IN THIS FORM 10K/A WERE PRESENTED IN OUR FORM 10-K,
WHICH WAS FILED ON MARCH 31, 2000.

     (A) LIST OF DOCUMENTS FILED AS PART OF THIS REPORT.

     2. FINANCIAL STATEMENT SCHEDULES.

Report of Other Auditor
        --Report of Chuo Audit Corporation on Asahi Komag Co., Ltd.

     All other schedules for which provision is made in the applicable
accounting regulation of the Securities and Exchange Commission were previously
filed in our Form 10-K on March 31, 2000, are not required under the related
instructions or are inapplicable and therefore have been omitted.

     3. EXHIBITS.

23.1     Consent of Ernst & Young LLP, independent auditors.

23.2     Consent of Chuo Audit Corporation.





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SIGNATURES

     PURSUANT TO THE REQUIREMENTS OF SECTION 13 OR 15(d) OF THE SECURITIES
EXCHANGE ACT OF 1934, REGISTRANT HAS DULY CAUSED THIS REPORT TO BE SIGNED ON ITS
BEHALF BY THE UNDERSIGNED, THEREUNTO DULY AUTHORIZED, IN SAN JOSE, CALIFORNIA ON
THIS 27TH DAY OF SEPTEMBER, 2000.

                                           Komag, Incorporated

                                           By   /s/Thian Hoo Tan
                                                ----------------------------
                                                Thian Hoo Tan
                                           President and Chief Executive Officer





                                       2
<PAGE>   5
     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES EXCHANGE ACT OF 1934, THIS
REPORT HAS BEEN SIGNED BY THE FOLLOWING PERSONS IN THE CAPACITIES AND ON THE
DATES INDICATED:

<TABLE>
<CAPTION>
          SIGNATURE                                TITLE                                  DATE
 ------------------------------    ------------------------------------------       -----------------
<S>                                <C>                                              <C>
                                    President, Chief Executive                       September 27, 2000
By: /s/ THIAN HOO TAN                Officer and Director
    ---------------------------     (Principal Executive Officer)
       (Thian Hoo Tan)

By: /s/ EDWARD H. SIEGLER           Vice President, Chief Financial Officer          September 27, 2000
    ---------------------------     and Secretary (Principal Financial Officer)
       (Edward H. Siegler)

By: /s/ KATHLEEN A. BAYLESS         Vice President, Corporate Controller             September 27, 2000
    ---------------------------     (Principal Accounting Officer)
       (Kathleen A. Bayless)

By:             *                   Director                                         September 27, 2000
    ---------------------------
          (Chris A. Eyre)

By:             *                   Director                                         September 27, 2000
    ---------------------------
        (Irwin Federman)

By:             *                   Director                                         September 27, 2000
    ---------------------------
         (George A. Neil)

By:             *                   Director                                         September 27, 2000
    ---------------------------
       (Michael R. Splinter)

By:             *                   Director                                         September 27, 2000
    ---------------------------
          (Anthony Sun)

By:             *                   Director                                         September 27, 2000
    ---------------------------
      (Masayoshi Takebayashi)

* By: /s/ THIAN HOO TAN                                                              September 27, 2000
    ---------------------------
        (Thian Hoo Tan,
         Attorney-in-Fact)
</TABLE>


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<PAGE>   6
                        REPORT OF INDEPENDENT ACCOUNTANTS

To the Board of Directors
Asahi Komag Co., Ltd.

     We have audited the accompanying consolidated balance sheets of Asahi Komag
Co., Ltd. and its subsidiary (the "Company") as of December 31, 1998 and 1997,
and the consolidated statements of income, cash flows, and changes in equity for
the years ended December 31, 1998, 1997 and 1996. These financial statements are
the responsibility of the Company's management. Our responsibility is to express
an opinion on these financial statements based on our audits.

     We conducted our audits in accordance with auditing standards generally
accepted in the United States of America. These standards require that we plan
and perform the audit to obtain reasonable assurance about whether the financial
statements are free of material misstatement. An audit includes examining, on a
test basis, evidence supporting the amounts and disclosures in the financial
statements. An audit also includes assessing the accounting principles used and
significant estimates made by management, as well as evaluating the overall
financial statement presentation. We believe that our audits provide a
reasonable basis for our opinion.

     In our opinion, based on our audit, the financial statements referred to
above present fairly, in all material respects, the consolidated financial
position of the Company as of December 31, 1998 and 1997, and the consolidated
results of its operations and its cash flows for the years ended December 31,
1998, 1997 and 1996 in conformity with generally accepted accounting principles
applicable in the United States of America.

     The accompanying financial statements have been prepared assuming that the
Company will continue as a going concern. As discussed in Note 14 to the
financial statements, the Company's directors have decided that it may be
necessary to wind-up the Company if additional cash cannot be obtained and debt
cannot be restructured. The financial statements do not include any adjustments
that could be material that might result from the outcome of this uncertainty.

     The consolidated financial statements as of and for the year ended December
31, 1998 have been translated into United States Dollars solely for the
convenience of the reader. Our audit included the translation, and in our
opinion such translation has been made in accordance with the basis stated in
note 2h to the consolidated financial statements.


                                            /s/ CHUO AUDIT CORPORATION

     Tokyo, Japan

     January 22, 1999, except for the matter discussed in the fourth paragraph
and Note 14, as to which the date is August 15, 2000


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