<PAGE>   1
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   FORM 10-Q/A

(Mark One)

[X]  Quarterly report pursuant to Section 13 or 15(d) of the Securities Exchange
     Act of 1934 for the quarterly period ended March 29, 1998 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:0-15086

                             SUN MICROSYSTEMS, INC.
             (Exact Name of registrant as specified in its charter)

<TABLE>
<S>                                                                        <C>       
               DELAWARE                                                               94-2805249
(State or other jurisdiction of incorporation or organization)             (I.R.S. Employer Identification No.)
</TABLE>

                    901 SAN ANTONIO ROAD, PALO ALTO, CA 94303
             (Address of principal executive offices with zip code)

       Registrant's telephone number, including area code: (650) 960-1300

                                       N/A
              (Former name, former address and former fiscal year,
                         if changed since last report)

        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 [ ]

                     APPLICABLE ONLY TO ISSUERS INVOLVED IN
                          BANKRUPTCY PROCEEDINGS DURING
                            THE PRECEDING FIVE YEARS:

        Indicate by check mark whether the registrant has filed all documents
and reports required to be filed by Section 12, 13 or 15(d) of the Securities
Exchange Act of 1934 subsequent to the distribution of securities under a plan
confirmed by a court.

                                 YES [ ] NO [ ]

                      APPLICABLE ONLY TO CORPORATE ISSUERS:

        Indicate the number of shares outstanding of each of the issuer's
classes of common stock, as of the latest practical date.


<TABLE>
<CAPTION>
              CLASS                                OUTSTANDING AT MARCH 29, 1998
              -----                                -----------------------------
<S>                                                <C>        
  Common stock - $0.00067 par value                       378,811,393
</TABLE>


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                                   SIGNATURES


Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.



                                SUN MICROSYSTEMS, INC.



                                BY

                                   /s/    Michael E. Lehman
                                   ------------------------------------------
                                   Michael E. Lehman
                                   Vice President, Corporate Resources and
                                   Chief Financial Officer



                                   /s/     George Reyes
                                   ------------------------------------------
                                   George Reyes
                                   Vice President and Corporate Controller,
                                   Chief Accounting Officer



Dated: July 15, 1998



                                       18


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                                  EXHIBIT INDEX


               27        Amended Financial Data Schedule