<PAGE>

The Index to Exhibits is on Page 6 of this document

        As filed with the Securities and Exchange Commission on December 3, 1999
                                         Registration No. ______________________
================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


                                    FORM S-8
                             REGISTRATION STATEMENT

                                      UNDER
                           THE SECURITIES ACT OF 1933


                                  ADAPTEC, INC.
             (Exact name of Registrant as specified in its charter)


          Delaware                                    94-2748530
 ------------------------                         -------------------
 (State of incorporation)             (I.R.S. Employer Identification Number)

                             691 Milpitas Boulevard
                           Milpitas, California 95035
                    (Address of principal executive offices)

                          ADAPTEC, INC. 1999 STOCK PLAN
                            (Full title of the Plan)

                               ROBERT N. STEPHENS
                      President and Chief Executive Officer
                                  ADAPTEC, INC.
                             691 Milpitas Boulevard
                           Milpitas, California 95035
                                 (408) 945-8600
            (Name, address and telephone number of agent for service)

                                   COPIES TO:
                           HENRY P. MASSEY, JR., 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>
                                                   Amount             Proposed Maximum       Proposed Maximum         Amount of
         Title of Securities to                    to be               Offering Price            Aggregate           Registration
             be Registered                     Registered(1)              Per Share           Offering Price             Fee
----------------------------------------- ------------------------- ---------------------- ---------------------- -----------------
<S>                                            <C>                    <C>                    <C>                     <C>
 Common Stock
   $0.001 par value, to be
   issued under the Adaptec,
   Inc. 1999 Stock Plan                             1,000,000           $54.375(2)             $54,375,000             $14,355
----------------------------------------- ------------------------- ---------------------- ---------------------- -----------------
</TABLE>

(1)  For the sole purpose of calculating the registration fee, the number of
     shares to be registered under this Registration Statement is the number of
     additional shares authorized to be issued under the Adaptec, Inc. 1999
     Stock Plan.

(2)  Estimated in accordance with Rule 457(h) under the Securities Act of 1933,
     as amended (the "Securities Act") solely for the purpose of calculating the
     registration fee. Computation based upon the average of the high and low
     prices of the Registrant's Common Stock as reported on The Nasdaq National
     Market on December 1, 1999 because the price at which options to be
     granted in the future may be exercised is not currently determinable.



<PAGE>

           PART II: INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.           INFORMATION INCORPORATED BY REFERENCE

                  The following documents and information heretofore filed with
the Securities and Exchange Commission (the "Commission") are hereby
incorporated by reference:

         (a)      The Registrant's Annual Report on Form 10-K, Commission file
                  no. 0-15071, filed on June 29, 1999.

         (b)      Quarterly reports on Form 10-Q/A relating to the quarters
                  ending June 30, 1998, September 30, 1998 and December 31, 1998
                  filed on July 7, 1999. Quarterly Reports on Form 10-Q relating
                  to the quarters ending June 30, 1999 and September 30, 1999
                  filed on August 12, 1999 and November 8, 1999, respectively.

         (c)      Items 1 and 2 of the Registrant's Registration Statement
                  Amendment on Form 8-A filed on July 20, 1992 pursuant to
                  Section 12 of the Securities and Exchange Act of 1934, as
                  amended (the "Exchange Act").

                  Exhibit 1 to Amendment No. 4 on Form 8-A (filed on January 14,
                  1997) to the Registrant's Registration Statement on Form 8-A,
                  Commission file no. 0-15071, filed on May 11, 1989.

                  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 which indicates that all securities offered have been
sold or which deregisters all securities then remaining unsold, shall be deemed
to be incorporated by reference in this Registration Statement and to be 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.

ITEM 6.           INDEMNIFICATION OF DIRECTORS AND OFFICERS

                  The Company's Certificate of Incorporation limits the
liability of directors to the maximum extent permitted by Delaware law. Delaware
law provides that directors of a corporation will not be personally liable for
monetary damages for breach of their fiduciary duties as directors, except for
liability (i) for any breach of their duty of loyalty to the corporation or its
stockholders, (ii) for acts or omissions not in good faith or that involve
intentional misconduct or a knowing violation of law, (iii) for unlawful
payments of dividends or unlawful stock repurchases or redemptions as provided
in Section 174 of the Delaware General Corporation Law, or (iv) for any
transaction from which the director derived an improper personal benefit.

                  The Company's Bylaws provide that the Company shall
indemnify its directors and officers and may indemnify its employees and
other agents to the fullest extent permitted by law. The Company's Bylaws
also permit the Company to secure insurance on behalf of any officer,
director, employee or other

                                      -1-

<PAGE>

agent for any liability arising out of his or her actions in such
capacity, regardless of whether the Company would have the power to indemnify
him or her against such liability under the General Corporation Law of Delaware.
The Company currently has secured such insurance on behalf of its officers and
directors.

                  The Company has entered into agreements to indemnify its
directors and officers, in addition to indemnification provided for in the
Company's Bylaws. Subject to certain conditions, these agreements, among other
things, indemnify the Company's directors and officers for certain expenses
(including attorneys' fees), judgments, fines and settlement amounts incurred by
any such person in any action or proceeding, including any action by or in the
right of the Company, arising out of such person's services as a director or
officer of the Company, any subsidiary of the Company or any other company or
enterprise to which the person provides services at the request of the Company.

ITEM 7.           EXEMPTION FROM REGISTRATION CLAIMED

                  Not applicable.

ITEM 8.           EXHIBITS

<TABLE>

                  <S>       <C>
                   4.1(1)   Second Amended and Restated Rights Agreement, dated
                            as of December 5, 1996 between Adaptec, Inc. and
                            ChaseMellon Shareholder Services, LLC, New York, NY,
                            including the Certificate of Determination, the form
                            of Rights Certificate and the Summary of Rights
                            attached thereto as Exhibits A, B and C,
                            respectively.

                   4.2(2)   First Amendment, dated March 12, 1998, to the Second
                            Amended and Restated Rights Agreement, dated as of
                            December 5, 1996 between Adaptec, Inc. and
                            ChaseMellon Shareholder Services, LLC, New York, NY,
                            including the Certificate of Determination, the form
                            of Rights Certificate and the Summary of Rights
                            attached thereto as Exhibits A, B and C,
                            respectively.

                   5.1      Opinion of Wilson Sonsini Goodrich & Rosati,
                            Professional Corporation, as to legality of
                            securities being registered.

                  23.1      Consent of Independent Accountants.

                  23.2      Consent of Wilson Sonsini Goodrich & Rosati,
                            Professional Corporation (see Exhibit 5.1).

                  24.1      Power of Attorney (see Page 4).
</TABLE>
                  -------------------------------------
                  (1) Incorporated by reference to Exhibit 1 to Amendment No. 4
                      on Form 8-A (filed January 14, 1997) to the Registrant's
                      Registration Statement (Commission File No. 0-15071) on
                      Form 8-A filed with the Commission on May 11, 1989.

                  (2) Incorporated by reference to Exhibit 4.2 to the
                      Registrant's Annual Report on Form 10-K, Commission file
                      no. 0-15071, filed on June 26, 1998.

ITEM 9.           UNDERTAKINGS

         A.       The undersigned Registrant hereby undertakes:

                                      -2-

<PAGE>
                  (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, 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, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) 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 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 Commission such
indemnification is against public policy as expressed in the Securities 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 Securities Act and will be governed by the final
adjudication of such issue.

                                      -3-


<PAGE>

                                   SIGNATURES

         Pursuant to the requirements of the Securities Act, 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 Amendment No. 1 to
be signed on its behalf by the undersigned, thereunto duly authorized, in the
City of Milpitas, State of California, on the 1st day of December, 1999.

                              ADAPTEC, INC.


                              By: /s/ ROBERT N. STEPHENS
                                 -----------------------------------------------
                                 Robert N. Stephens
                                 PRESIDENT, CHIEF EXECUTIVE OFFICER AND DIRECTOR

                                      -4-

<PAGE>

                                POWER OF ATTORNEY

         KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Robert N. Stephens and Andrew J. Brown,
jointly and severally, as his attorneys-in-fact, each with the power of
substitution, for him in any and all capacities, to sign any amendments to this
Registration Statement on Form S-8, and to file the same, with exhibits thereto
and other documents in connection therewith, with the Securities and Exchange
Commission, hereby ratifying and confirming all that each of said
attorneys-in-fact, or his substitute or substitutes may do or cause to be done
by virtue hereof.

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.

<TABLE>
<CAPTION>
                    Name                                            Title                           Date
--------------------------------------------- ---------------------------------------------- ------------------
<S>                                           <C>                                            <C>
/s/ ROBERT N. STEPHENS                        President, Chief Executive Officer and          December 1, 1999
--------------------------------------------- Director
Robert N. Stephens

/s/ ANDREW J. BROWN                           Vice President, Chief Financial Officer and     December 1, 1999
--------------------------------------------- Assistant Secretary (Principal Financial
Andrew J. Brown                               Officer)

/s/ KENNETH B. AROLA                          Vice President and Corporate Controller         December 1, 1999
--------------------------------------------- (Principal Accounting Officer)
Kenneth B. Arola

/s/ JOHN G. ADLER                             Director                                        December 1, 1999
---------------------------------------------
John G. Adler

/s/ LAURENCE B. BOUCHER                       Chairman of the Board and Director              December 1, 1999
---------------------------------------------
Laurence B. Boucher

/s/ CARL J. CONTI                             Director                                        December 1, 1999
---------------------------------------------
Carl J. Conti

/s/ JOHN EAST                                 Director                                        December 1, 1999
---------------------------------------------
John East

/s/ ILENE H. LANG                             Director                                        December 1, 1999
---------------------------------------------
Ilene H. Lang

/s/ ROBERT J. LOARIE                          Director                                        December 1, 1999
---------------------------------------------
Robert J. Loarie

/s/ B.J. MOORE                                Director                                        December 1, 1999
---------------------------------------------
B.J. Moore

/s/ W. FERRELL SANDERS                        Director                                        December 1, 1999
---------------------------------------------
W. Ferrell Sanders

/s/ PHILLIP E. WHITE                          Director                                        December 1, 1999
---------------------------------------------
Phillip E. White

</TABLE>
                                      -5-

<PAGE>

                              INDEX TO EXHIBITS

<TABLE>
<CAPTION>

         EXHIBIT
         NUMBER                                                                            PAGE NO.
-------------------------                                                                 ----------
         <S>               <C>                                                             <C>
           4.1(1)          Second Amended and Restated Rights Agreement, dated
                           as of December 5, 1996 between Adaptec, Inc. and
                           ChaseMellon Shareholder Services, LLC, New York, NY,
                           including the Certificate of Determination, the form
                           of Rights Certificate and the Summary of Rights
                           attached thereto as Exhibits A, B and C,
                           respectively.

           4.2(2)          First Amendment, dated March 12, 1998, to the Second
                           Amended and Restated Rights Agreement, dated as of
                           December 5, 1996 between Adaptec, Inc. and
                           ChaseMellon Shareholder Services, LLC, New York, NY,
                           including the Certificate of Determination, the form
                           of Rights Certificate and the Summary of Rights
                           attached thereto as Exhibits A, B and C,
                           respectively.

           5.1             Opinion of Wilson Sonsini Goodrich & Rosati,
                           Professional Corporation, as to legality of
                           securities being registered.

          23.1             Consent of Independent Accountants

          23.2             Consent of Wilson Sonsini Goodrich & Rosati, Professional Corporation (see
                           Exhibit 5.1).
</TABLE>
---------------------------------------------

         (1)  Incorporated by reference to Exhibit 1 to Amendment No. 4 on Form
              8-A (filed January 14, 1997) to the Registrant's Registration
              Statement (Commission File No. 0-15071) on Form 8-A filed with the
              Commission on May 11, 1989.

         (2)  Incorporated by reference to Exhibit 4.2 to the Registrant's
              Annual Report on Form 10-K (Commission file no. 0-15071) filed
              with the Commission on June 26, 1998.

                                      -6-
[{"type": "S-8", "sequence": "1", "description": "S-8", "secsgml_size_bytes": 20026}]
{"company-data": {"conformed-name": "ADAPTEC INC", "cik": "0000709804", "assigned-sic": "3576", "irs-number": "942748530", "state-of-incorporation": "DE", "fiscal-year-end": "0331"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-92173", "film-number": "99769504"}, "business-address": {"street1": "691 S MILPITAS BLVD", "street2": "M/S25", "city": "MILPITAS", "state": "CA", "zip": "95035", "phone": "4089458600"}, "mail-address": {"street1": "691 SOUTH MILPITAS BLVD", "street2": "M/S25", "city": "MILPITAS", "state": "CA", "zip": "95035"}}
The Index to Exhibits is on Page 6 of this document

        As filed with the Securities and Exchange Commission on December 3, 1999
                                         Registration No. ______________________
================================================================================
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENT

                                      UNDER
                           THE SECURITIES ACT OF 1933

                                  ADAPTEC, INC.
             (Exact name of Registrant as specified in its charter)

          Delaware                                    94-2748530
 ------------------------                         -------------------
 (State of incorporation)             (I.R.S. Employer Identification Number)

                             691 Milpitas Boulevard
                           Milpitas, California 95035
                    (Address of principal executive offices)

                          ADAPTEC, INC. 1999 STOCK PLAN
                            (Full title of the Plan)

                               ROBERT N. STEPHENS
                      President and Chief Executive Officer
                                  ADAPTEC, INC.
                             691 Milpitas Boulevard
                           Milpitas, California 95035
                                 (408) 945-8600
            (Name, address and telephone number of agent for service)

                                   COPIES TO:
                           HENRY P. MASSEY, JR., ESQ.
                        Wilson Sonsini Goodrich & Rosati
                            Professional Corporation
                               650 Page Mill Road
                        Palo Alto, California 94304-1050
                                 (650) 493-9300

================================================================================
================================================================================
                         CALCULATION OF REGISTRATION FEE
================================================================================
Amount             Proposed Maximum       Proposed Maximum         Amount of
         Title of Securities to                    to be               Offering Price            Aggregate           Registration
             be Registered                     Registered(1)              Per Share           Offering Price             Fee
----------------------------------------- ------------------------- ---------------------- ---------------------- -----------------
Common Stock
   $0.001 par value, to be
   issued under the Adaptec,
   Inc. 1999 Stock Plan                             1,000,000           $54.375(2)             $54,375,000             $14,355
----------------------------------------- ------------------------- ---------------------- ---------------------- -----------------
(1)  For the sole purpose of calculating the registration fee, the number of
     shares to be registered under this Registration Statement is the number of
     additional shares authorized to be issued under the Adaptec, Inc. 1999
     Stock Plan.

(2)  Estimated in accordance with Rule 457(h) under the Securities Act of 1933,
     as amended (the "Securities Act") solely for the purpose of calculating the
     registration fee. Computation based upon the average of the high and low
     prices of the Registrant's Common Stock as reported on The Nasdaq National
     Market on December 1, 1999 because the price at which options to be
     granted in the future may be exercised is not currently determinable.
PART II: INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.           INFORMATION INCORPORATED BY REFERENCE

                  The following documents and information heretofore filed with
the Securities and Exchange Commission (the "Commission") are hereby
incorporated by reference:

         (a)      The Registrant's Annual Report on Form 10-K, Commission file
                  no. 0-15071, filed on June 29, 1999.

         (b)      Quarterly reports on Form 10-Q/A relating to the quarters
                  ending June 30, 1998, September 30, 1998 and December 31, 1998
                  filed on July 7, 1999. Quarterly Reports on Form 10-Q relating
                  to the quarters ending June 30, 1999 and September 30, 1999
                  filed on August 12, 1999 and November 8, 1999, respectively.

         (c)      Items 1 and 2 of the Registrant's Registration Statement
                  Amendment on Form 8-A filed on July 20, 1992 pursuant to
                  Section 12 of the Securities and Exchange Act of 1934, as
                  amended (the "Exchange Act").

                  Exhibit 1 to Amendment No. 4 on Form 8-A (filed on January 14,
                  1997) to the Registrant's Registration Statement on Form 8-A,
                  Commission file no. 0-15071, filed on May 11, 1989.

                  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 which indicates that all securities offered have been
sold or which deregisters all securities then remaining unsold, shall be deemed
to be incorporated by reference in this Registration Statement and to be 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.

ITEM 6.           INDEMNIFICATION OF DIRECTORS AND OFFICERS

                  The Company's Certificate of Incorporation limits the
liability of directors to the maximum extent permitted by Delaware law. Delaware
law provides that directors of a corporation will not be personally liable for
monetary damages for breach of their fiduciary duties as directors, except for
liability (i) for any breach of their duty of loyalty to the corporation or its
stockholders, (ii) for acts or omissions not in good faith or that involve
intentional misconduct or a knowing violation of law, (iii) for unlawful
payments of dividends or unlawful stock repurchases or redemptions as provided
in Section 174 of the Delaware General Corporation Law, or (iv) for any
transaction from which the director derived an improper personal benefit.

                  The Company's Bylaws provide that the Company shall
indemnify its directors and officers and may indemnify its employees and
other agents to the fullest extent permitted by law. The Company's Bylaws
also permit the Company to secure insurance on behalf of any officer,
director, employee or other

                                      -1-
agent for any liability arising out of his or her actions in such
capacity, regardless of whether the Company would have the power to indemnify
him or her against such liability under the General Corporation Law of Delaware.
The Company currently has secured such insurance on behalf of its officers and
directors.

                  The Company has entered into agreements to indemnify its
directors and officers, in addition to indemnification provided for in the
Company's Bylaws. Subject to certain conditions, these agreements, among other
things, indemnify the Company's directors and officers for certain expenses
(including attorneys' fees), judgments, fines and settlement amounts incurred by
any such person in any action or proceeding, including any action by or in the
right of the Company, arising out of such person's services as a director or
officer of the Company, any subsidiary of the Company or any other company or
enterprise to which the person provides services at the request of the Company.

ITEM 7.           EXEMPTION FROM REGISTRATION CLAIMED

                  Not applicable.

ITEM 8.           EXHIBITS
4.1(1)   Second Amended and Restated Rights Agreement, dated
                            as of December 5, 1996 between Adaptec, Inc. and
                            ChaseMellon Shareholder Services, LLC, New York, NY,
                            including the Certificate of Determination, the form
                            of Rights Certificate and the Summary of Rights
                            attached thereto as Exhibits A, B and C,
                            respectively.

                   4.2(2)   First Amendment, dated March 12, 1998, to the Second
                            Amended and Restated Rights Agreement, dated as of
                            December 5, 1996 between Adaptec, Inc. and
                            ChaseMellon Shareholder Services, LLC, New York, NY,
                            including the Certificate of Determination, the form
                            of Rights Certificate and the Summary of Rights
                            attached thereto as Exhibits A, B and C,
                            respectively.

                   5.1      Opinion of Wilson Sonsini Goodrich & Rosati,
                            Professional Corporation, as to legality of
                            securities being registered.

                  23.1      Consent of Independent Accountants.

                  23.2      Consent of Wilson Sonsini Goodrich & Rosati,
                            Professional Corporation (see Exhibit 5.1).

                  24.1      Power of Attorney (see Page 4).
-------------------------------------
                  (1) Incorporated by reference to Exhibit 1 to Amendment No. 4
                      on Form 8-A (filed January 14, 1997) to the Registrant's
                      Registration Statement (Commission File No. 0-15071) on
                      Form 8-A filed with the Commission on May 11, 1989.

                  (2) Incorporated by reference to Exhibit 4.2 to the
                      Registrant's Annual Report on Form 10-K, Commission file
                      no. 0-15071, filed on June 26, 1998.

ITEM 9.           UNDERTAKINGS

         A.       The undersigned Registrant hereby undertakes:

                                      -2-
(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, 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, each filing of the
Registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Exchange Act (and, where applicable, each filing of an employee benefit plan's
annual report pursuant to Section 15(d) of the Exchange Act) 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 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 Commission such
indemnification is against public policy as expressed in the Securities 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 Securities Act and will be governed by the final
adjudication of such issue.

                                      -3-
SIGNATURES

         Pursuant to the requirements of the Securities Act, 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 Amendment No. 1 to
be signed on its behalf by the undersigned, thereunto duly authorized, in the
City of Milpitas, State of California, on the 1st day of December, 1999.

                              ADAPTEC, INC.

                              By: /s/ ROBERT N. STEPHENS
                                 -----------------------------------------------
                                 Robert N. Stephens
                                 PRESIDENT, CHIEF EXECUTIVE OFFICER AND DIRECTOR

                                      -4-
POWER OF ATTORNEY

         KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature
appears below constitutes and appoints Robert N. Stephens and Andrew J. Brown,
jointly and severally, as his attorneys-in-fact, each with the power of
substitution, for him in any and all capacities, to sign any amendments to this
Registration Statement on Form S-8, and to file the same, with exhibits thereto
and other documents in connection therewith, with the Securities and Exchange
Commission, hereby ratifying and confirming all that each of said
attorneys-in-fact, or his substitute or substitutes may do or cause to be done
by virtue hereof.

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities and on the date indicated.
Name                                            Title                           Date
--------------------------------------------- ---------------------------------------------- ------------------
/s/ ROBERT N. STEPHENS                        President, Chief Executive Officer and          December 1, 1999
--------------------------------------------- Director
Robert N. Stephens

/s/ ANDREW J. BROWN                           Vice President, Chief Financial Officer and     December 1, 1999
--------------------------------------------- Assistant Secretary (Principal Financial
Andrew J. Brown                               Officer)

/s/ KENNETH B. AROLA                          Vice President and Corporate Controller         December 1, 1999
--------------------------------------------- (Principal Accounting Officer)
Kenneth B. Arola

/s/ JOHN G. ADLER                             Director                                        December 1, 1999
---------------------------------------------
John G. Adler

/s/ LAURENCE B. BOUCHER                       Chairman of the Board and Director              December 1, 1999
---------------------------------------------
Laurence B. Boucher

/s/ CARL J. CONTI                             Director                                        December 1, 1999
---------------------------------------------
Carl J. Conti

/s/ JOHN EAST                                 Director                                        December 1, 1999
---------------------------------------------
John East

/s/ ILENE H. LANG                             Director                                        December 1, 1999
---------------------------------------------
Ilene H. Lang

/s/ ROBERT J. LOARIE                          Director                                        December 1, 1999
---------------------------------------------
Robert J. Loarie

/s/ B.J. MOORE                                Director                                        December 1, 1999
---------------------------------------------
B.J. Moore

/s/ W. FERRELL SANDERS                        Director                                        December 1, 1999
---------------------------------------------
W. Ferrell Sanders

/s/ PHILLIP E. WHITE                          Director                                        December 1, 1999
---------------------------------------------
Phillip E. White
-5-
INDEX TO EXHIBITS
EXHIBIT
         NUMBER                                                                            PAGE NO.
-------------------------                                                                 ----------
4.1(1)          Second Amended and Restated Rights Agreement, dated
                           as of December 5, 1996 between Adaptec, Inc. and
                           ChaseMellon Shareholder Services, LLC, New York, NY,
                           including the Certificate of Determination, the form
                           of Rights Certificate and the Summary of Rights
                           attached thereto as Exhibits A, B and C,
                           respectively.

           4.2(2)          First Amendment, dated March 12, 1998, to the Second
                           Amended and Restated Rights Agreement, dated as of
                           December 5, 1996 between Adaptec, Inc. and
                           ChaseMellon Shareholder Services, LLC, New York, NY,
                           including the Certificate of Determination, the form
                           of Rights Certificate and the Summary of Rights
                           attached thereto as Exhibits A, B and C,
                           respectively.

           5.1             Opinion of Wilson Sonsini Goodrich & Rosati,
                           Professional Corporation, as to legality of
                           securities being registered.

          23.1             Consent of Independent Accountants

          23.2             Consent of Wilson Sonsini Goodrich & Rosati, Professional Corporation (see
                           Exhibit 5.1).
---------------------------------------------

         (1)  Incorporated by reference to Exhibit 1 to Amendment No. 4 on Form
              8-A (filed January 14, 1997) to the Registrant's Registration
              Statement (Commission File No. 0-15071) on Form 8-A filed with the
              Commission on May 11, 1989.

         (2)  Incorporated by reference to Exhibit 4.2 to the Registrant's
              Annual Report on Form 10-K (Commission file no. 0-15071) filed
              with the Commission on June 26, 1998.

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