<PAGE>

   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON DECEMBER 22, 1999

                                                   REGISTRATION NO. 333-
--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

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

                    ADVANCED DIGITAL INFORMATION CORPORATION
             (Exact name of Registrant as specified in its charter)

           WASHINGTON                                    91-1618616
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)

                               11431 WILLOWS ROAD
                                 P.O. BOX 97507
                         REDMOND, WASHINGTON 98073-9757
          (Address of principal executive offices, including zip code)

                    ADVANCED DIGITAL INFORMATION CORPORATION
                 1999 MOUNTAINGATE TRANSITION STOCK OPTION PLAN

                    ADVANCED DIGITAL INFORMATION CORPORATION
                             1996 STOCK OPTION PLAN
                            (Full title of the plans)

                               PETER H. VAN OPPEN
                             CHIEF EXECUTIVE OFFICER
                    ADVANCED DIGITAL INFORMATION CORPORATION
                               11431 WILLOWS ROAD
                                 P.O. BOX 97507
                         REDMOND, WASHINGTON 98073-9757
                                 (425) 881-8004
 (Name, address and telephone number, including area code, of agent for service)

                             ----------------------
                                    COPY TO:

                               LINDA A. SCHOEMAKER
                                PERKINS COIE LLP
                          1201 THIRD AVENUE, 48TH FLOOR
                         SEATTLE, WASHINGTON 98101-3099
                                 (206) 583-8888

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
-----------------------------------------------------------------------------------------------------------------
                                              AMOUNT TO      PROPOSED MAXIMUM    PROPOSED MAXIMUM    AMOUNT OF
           TITLE OF SECURITIES                   BE           OFFERING PRICE        AGGREGATE       REGISTRATION
            TO BE REGISTERED               REGISTERED(1)(2)     PER SHARE         OFFERING PRICE        FEE
-----------------------------------------------------------------------------------------------------------------
<S>                                        <C>               <C>                 <C>                <C>
COMMON STOCK, NO PAR VALUE, SUBJECT TO
OUTSTANDING OPTIONS UNDER THE:
-----------------------------------------------------------------------------------------------------------------
   1999 MOUNTAINGATE TRANSITION STOCK
   OPTION PLAN                                 172,222         $32.875 (3)         $5,661,798.20      $1,494.71
-----------------------------------------------------------------------------------------------------------------
   1996 STOCK OPTION PLAN                      943,272          $30.33 (4)        $28,609,439.00      $7,552.89
-----------------------------------------------------------------------------------------------------------------
COMMON STOCK, NO PAR VALUE, AUTHORIZED BUT
UNISSUED UNDER THE:
-----------------------------------------------------------------------------------------------------------------
   1999 MOUNTAINGATE TRANSITION STOCK
   OPTION PLAN                                  57,778          $51.19 (5)         $2,957,655.80        $780.82
-----------------------------------------------------------------------------------------------------------------
   1996 STOCK OPTION PLAN                      256,728          $51.19 (5)        $13,141,906.00      $3,469.46
-----------------------------------------------------------------------------------------------------------------
         TOTAL:                              1,430,000                            $50,370,799.00     $13,297.88
-----------------------------------------------------------------------------------------------------------------
</TABLE>

(1)      Includes associated Preferred Stock Purchase Rights.

<PAGE>

(2)      Together with an indeterminate number of additional shares which may be
         necessary to adjust the number of shares reserved for issuance pursuant
         to the plans as the result of any future stock split, stock dividend or
         similar adjustment of the Registrant's outstanding Common Stock.

(3)      Computed pursuant to Rule 457(h) under the Securities Act of 1933, as
         amended. The proposed maximum offering price of $32.875 represents the
         exercise price of currently outstanding option grants.

(4)      Computed pursuant to Rule 457(h) under the Securities Act of 1933, as
         amended. The proposed maximum offering price of $30.33 represents the
         weighted average of the exercise prices of currently outstanding option
         grants, which range from $6.70 per share to $55.438 per share.

(5)      Estimated pursuant to Rule 457(c) under the Securities Act of 1933, as
         amended, solely for the purpose of calculating the registration fee.
         The price per share under the plans is estimated to be $51.19 based on
         the average of the high ($52.1875) and low ($50.1875) sales prices for
         the Common Stock on December 20, 1999 as reported by the Nasdaq
         National Market.

<PAGE>

                                       PART II

                    INFORMATION REQUIRED IN REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

       The following documents filed with the Securities and Exchange
Commission (the "Commission") are hereby incorporated by reference in this
Registration Statement:

              (a)    The Registrant's Annual Report on Form 10-K and Form
10-K/A for the year ended October 31, 1998, filed on January 22, 1999 and
September 14, 1999, respectively, which contains audited financial statements
for the most recent fiscal year for which such statements have been filed;

              (b)    All other reports filed by the Registrant pursuant to
Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended
(the "Exchange Act"), since the end of the fiscal year covered by the Annual
Report on Form 10-K referred to in (a) above; and

              (c)    The description of the Registrant's Common Stock
contained in the Registrant's Registration Statement on Form 10 filed on July
29, 1996 under Section 12(g) of the Exchange Act, including any amendments or
reports filed for the purpose of updating such description.

       All documents filed by the Registrant pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Exchange Act after the date hereof and prior to
the filing of a post-effective amendment which indicates that the securities
offered hereby have been sold or which deregister the securities covered
hereby then remaining unsold, shall also be deemed to be incorporated by
reference into this Registration Statement and to be a part hereof commencing
on the respective dates on which such documents are filed.

ITEM 4.       DESCRIPTION OF SECURITIES

       Not applicable.

ITEM 5.       INTERESTS OF NAMED EXPERTS AND COUNSEL

       None.

ITEM 6.       INDEMNIFICATION OF DIRECTORS AND OFFICERS

       Sections 23B.08.500 through 23B.08.600 of the Washington Business
Corporation Act authorize a court to award, or a corporation's board of
directors to grant, indemnification to directors and officers on terms
sufficiently broad to permit indemnification under certain circumstances for
liabilities arising under the Securities Act of 1933, as amended (the
"Securities Act").  Section 10 of the Registrant's Restated Bylaws provides
for indemnification of the Registrant's directors, officers, employees and
agents to the maximum extent permitted by Washington law.

       Section 23B.08.320 of the Washington Business Corporation Act
authorizes a corporation to limit a director's liability to the corporation
or its shareholders for monetary damages for acts or omissions as a director,
except in certain circumstances involving intentional misconduct,
self-dealing or illegal corporate loans or distributions, or any transactions
from which the director personally receives a benefit in money, property or
services to which the director is not entitled.  Article 11 of the
Registrant's Restated Articles of Incorporation contains provisions
implementing, to the fullest extent permitted by Washington law, such
limitations on a director's liability to the Registrant and its shareholders.

       The Registrant also maintains an insurance policy insuring its
directors and officers against liability for certain acts or omissions while
acting in their official capacities.

ITEM 7.       EXEMPTION FROM REGISTRATION CLAIMED

       Not applicable.

                                        II-1

<PAGE>

ITEM 8.       EXHIBITS

<TABLE>
<CAPTION>

    Exhibit
     Number                               Description
------------    ---------------------------------------------------------------
     <S>        <C>
      5.1       Opinion of Perkins Coie LLP regarding legality of the Common
                Stock being registered

      23.1      Consent of PricewaterhouseCoopers LLP

      23.2      Consent of Perkins Coie LLP (included in opinion filed as
                Exhibit 5.1)

      24.1      Power of Attorney (see signature page)

      99.1      Advanced Digital Information Corporation 1999 MountainGate
                Transition Stock Option Plan

      99.2      Advanced Digital Information Corporation 1996 Stock Option Plan

</TABLE>


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;

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

              (iii)  To include any material information with respect to the
plan of distribution not previously disclosed in this Registration Statement
or any material change to such information in this Registration Statement;

PROVIDED, HOWEVER, that paragraphs (1)(i) and (1)(ii) above 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 Exchange Act that are
incorporated by reference in this 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 15(d) of the Exchange
Act (and, where applicable, each filing of an employee benefits plan's annual
report pursuant to Section 15(d) of the Exchange Act) that is incorporated by
reference in this 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.

                                        II-2

<PAGE>

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.

                                        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 Redmond, State of Washington, on
the 21st day of December 1999.

                                   ADVANCED DIGITAL INFORMATION CORPORATION

                                          /s/ PETER H. VAN OPPEN
                                   --------------------------------------------
                                   By:    Peter H. van Oppen
                                          Chairman and Chief Executive Officer

       Each person whose individual signature appears below hereby authorizes
Peter H. van Oppen and Charles H. Stonecipher, or either of them, as
attorneys-in-fact with full power of substitution, to execute in the name and
on the behalf of each person, individually and in each capacity stated below,
and to file, any and all post-effective amendments to this Registration
Statement.

       Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities indicated below on the 21st day of December 1999.

<TABLE>
<CAPTION>

              SIGNATURE                                 TITLE
<S>                                   <C>
        /s/ PETER H. VAN OPPEN        Chief Executive Officer and Chairman of
  ---------------------------------   the Board (Principal Executive Officer)
          Peter H. van Oppen

            /s/ JON GACEK             Chief Financial Officer (Principal
  ---------------------------------   Financial and Accounting Officer)
              Jon Gacek

          /s/ TOM A. ALBERG           Director
  ---------------------------------
            Tom A. Alberg

      /s/ CHRISTOPHER T. BAYLEY       Director
  ---------------------------------
        Christopher T. Bayley

        /s/ RUSSELL F. MCNEILL        Director
  ---------------------------------
          Russell F. McNeill

         /s/ JOHN W. STANTON          Director
  ---------------------------------
           John W. Stanton

         /s/ WALTER F. WALKER         Director
  ---------------------------------
           Walter F. Walker

</TABLE>

                                        II-4

<PAGE>

                               INDEX TO EXHIBITS

<TABLE>
<CAPTION>

    Exhibit
    Number                               Description
------------    ---------------------------------------------------------------
<S>             <C>
      5.1       Opinion of Perkins Coie LLP regarding legality of the Common
                Stock being registered

      23.1      Consent of PricewaterhouseCoopers LLP

      23.2      Consent of Perkins Coie LLP (included in opinion filed as
                Exhibit 5.1)

      24.1      Power of Attorney (see signature page)

      99.1      Advanced Digital Information Corporation 1999 MoutainGate
                Transition Stock Option Plan

      99.2      Advanced Digital Information Corporation 1996 Stock Option Plan

</TABLE>
[{"type": "S-8", "sequence": "1", "description": "FORM S-8", "secsgml_size_bytes": 17099}]
{"company-data": {"conformed-name": "ADVANCED DIGITAL INFORMATION CORP", "cik": "0000770403", "assigned-sic": "3577", "irs-number": "911618616", "state-of-incorporation": "WA", "fiscal-year-end": "1031"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-93429", "film-number": "99779252"}, "business-address": {"street1": "P O BOX 97057", "street2": "11431 WILLOWS RD", "city": "REDMOND", "state": "WA", "zip": "98073-9757", "phone": "4258818004"}, "mail-address": {"street1": "P.O. BOX 97057", "street2": "P O BOX 97057", "city": "REDMOND", "state": "WA", "zip": "98073-9757"}}
AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON DECEMBER 22, 1999

                                                   REGISTRATION NO. 333-
--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

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

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

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

                    ADVANCED DIGITAL INFORMATION CORPORATION
             (Exact name of Registrant as specified in its charter)

           WASHINGTON                                    91-1618616
(State or other jurisdiction of             (I.R.S. Employer Identification No.)
incorporation or organization)

                               11431 WILLOWS ROAD
                                 P.O. BOX 97507
                         REDMOND, WASHINGTON 98073-9757
          (Address of principal executive offices, including zip code)

                    ADVANCED DIGITAL INFORMATION CORPORATION
                 1999 MOUNTAINGATE TRANSITION STOCK OPTION PLAN

                    ADVANCED DIGITAL INFORMATION CORPORATION
                             1996 STOCK OPTION PLAN
                            (Full title of the plans)

                               PETER H. VAN OPPEN
                             CHIEF EXECUTIVE OFFICER
                    ADVANCED DIGITAL INFORMATION CORPORATION
                               11431 WILLOWS ROAD
                                 P.O. BOX 97507
                         REDMOND, WASHINGTON 98073-9757
                                 (425) 881-8004
 (Name, address and telephone number, including area code, of agent for service)

                             ----------------------
                                    COPY TO:

                               LINDA A. SCHOEMAKER
                                PERKINS COIE LLP
                          1201 THIRD AVENUE, 48TH FLOOR
                         SEATTLE, WASHINGTON 98101-3099
                                 (206) 583-8888

                         CALCULATION OF REGISTRATION FEE
-----------------------------------------------------------------------------------------------------------------
                                              AMOUNT TO      PROPOSED MAXIMUM    PROPOSED MAXIMUM    AMOUNT OF
           TITLE OF SECURITIES                   BE           OFFERING PRICE        AGGREGATE       REGISTRATION
            TO BE REGISTERED               REGISTERED(1)(2)     PER SHARE         OFFERING PRICE        FEE
-----------------------------------------------------------------------------------------------------------------
COMMON STOCK, NO PAR VALUE, SUBJECT TO
OUTSTANDING OPTIONS UNDER THE:
-----------------------------------------------------------------------------------------------------------------
   1999 MOUNTAINGATE TRANSITION STOCK
   OPTION PLAN                                 172,222         $32.875 (3)         $5,661,798.20      $1,494.71
-----------------------------------------------------------------------------------------------------------------
   1996 STOCK OPTION PLAN                      943,272          $30.33 (4)        $28,609,439.00      $7,552.89
-----------------------------------------------------------------------------------------------------------------
COMMON STOCK, NO PAR VALUE, AUTHORIZED BUT
UNISSUED UNDER THE:
-----------------------------------------------------------------------------------------------------------------
   1999 MOUNTAINGATE TRANSITION STOCK
   OPTION PLAN                                  57,778          $51.19 (5)         $2,957,655.80        $780.82
-----------------------------------------------------------------------------------------------------------------
   1996 STOCK OPTION PLAN                      256,728          $51.19 (5)        $13,141,906.00      $3,469.46
-----------------------------------------------------------------------------------------------------------------
         TOTAL:                              1,430,000                            $50,370,799.00     $13,297.88
-----------------------------------------------------------------------------------------------------------------
(1)      Includes associated Preferred Stock Purchase Rights.
(2)      Together with an indeterminate number of additional shares which may be
         necessary to adjust the number of shares reserved for issuance pursuant
         to the plans as the result of any future stock split, stock dividend or
         similar adjustment of the Registrant's outstanding Common Stock.

(3)      Computed pursuant to Rule 457(h) under the Securities Act of 1933, as
         amended. The proposed maximum offering price of $32.875 represents the
         exercise price of currently outstanding option grants.

(4)      Computed pursuant to Rule 457(h) under the Securities Act of 1933, as
         amended. The proposed maximum offering price of $30.33 represents the
         weighted average of the exercise prices of currently outstanding option
         grants, which range from $6.70 per share to $55.438 per share.

(5)      Estimated pursuant to Rule 457(c) under the Securities Act of 1933, as
         amended, solely for the purpose of calculating the registration fee.
         The price per share under the plans is estimated to be $51.19 based on
         the average of the high ($52.1875) and low ($50.1875) sales prices for
         the Common Stock on December 20, 1999 as reported by the Nasdaq
         National Market.
PART II

                    INFORMATION REQUIRED IN REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

       The following documents filed with the Securities and Exchange
Commission (the "Commission") are hereby incorporated by reference in this
Registration Statement:

              (a)    The Registrant's Annual Report on Form 10-K and Form
10-K/A for the year ended October 31, 1998, filed on January 22, 1999 and
September 14, 1999, respectively, which contains audited financial statements
for the most recent fiscal year for which such statements have been filed;

              (b)    All other reports filed by the Registrant pursuant to
Section 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended
(the "Exchange Act"), since the end of the fiscal year covered by the Annual
Report on Form 10-K referred to in (a) above; and

              (c)    The description of the Registrant's Common Stock
contained in the Registrant's Registration Statement on Form 10 filed on July
29, 1996 under Section 12(g) of the Exchange Act, including any amendments or
reports filed for the purpose of updating such description.

       All documents filed by the Registrant pursuant to Sections 13(a),
13(c), 14 and 15(d) of the Exchange Act after the date hereof and prior to
the filing of a post-effective amendment which indicates that the securities
offered hereby have been sold or which deregister the securities covered
hereby then remaining unsold, shall also be deemed to be incorporated by
reference into this Registration Statement and to be a part hereof commencing
on the respective dates on which such documents are filed.

ITEM 4.       DESCRIPTION OF SECURITIES

       Not applicable.

ITEM 5.       INTERESTS OF NAMED EXPERTS AND COUNSEL

       None.

ITEM 6.       INDEMNIFICATION OF DIRECTORS AND OFFICERS

       Sections 23B.08.500 through 23B.08.600 of the Washington Business
Corporation Act authorize a court to award, or a corporation's board of
directors to grant, indemnification to directors and officers on terms
sufficiently broad to permit indemnification under certain circumstances for
liabilities arising under the Securities Act of 1933, as amended (the
"Securities Act").  Section 10 of the Registrant's Restated Bylaws provides
for indemnification of the Registrant's directors, officers, employees and
agents to the maximum extent permitted by Washington law.

       Section 23B.08.320 of the Washington Business Corporation Act
authorizes a corporation to limit a director's liability to the corporation
or its shareholders for monetary damages for acts or omissions as a director,
except in certain circumstances involving intentional misconduct,
self-dealing or illegal corporate loans or distributions, or any transactions
from which the director personally receives a benefit in money, property or
services to which the director is not entitled.  Article 11 of the
Registrant's Restated Articles of Incorporation contains provisions
implementing, to the fullest extent permitted by Washington law, such
limitations on a director's liability to the Registrant and its shareholders.

       The Registrant also maintains an insurance policy insuring its
directors and officers against liability for certain acts or omissions while
acting in their official capacities.

ITEM 7.       EXEMPTION FROM REGISTRATION CLAIMED

       Not applicable.

                                        II-1
ITEM 8.       EXHIBITS
Exhibit
     Number                               Description
------------    ---------------------------------------------------------------
5.1       Opinion of Perkins Coie LLP regarding legality of the Common
                Stock being registered

      23.1      Consent of PricewaterhouseCoopers LLP

      23.2      Consent of Perkins Coie LLP (included in opinion filed as
                Exhibit 5.1)

      24.1      Power of Attorney (see signature page)

      99.1      Advanced Digital Information Corporation 1999 MountainGate
                Transition Stock Option Plan

      99.2      Advanced Digital Information Corporation 1996 Stock Option Plan
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;

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

              (iii)  To include any material information with respect to the
plan of distribution not previously disclosed in this Registration Statement
or any material change to such information in this Registration Statement;

PROVIDED, HOWEVER, that paragraphs (1)(i) and (1)(ii) above 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 Exchange Act that are
incorporated by reference in this 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 15(d) of the Exchange
Act (and, where applicable, each filing of an employee benefits plan's annual
report pursuant to Section 15(d) of the Exchange Act) that is incorporated by
reference in this 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.

                                        II-2
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.

                                        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 Redmond, State of Washington, on
the 21st day of December 1999.

                                   ADVANCED DIGITAL INFORMATION CORPORATION

                                          /s/ PETER H. VAN OPPEN
                                   --------------------------------------------
                                   By:    Peter H. van Oppen
                                          Chairman and Chief Executive Officer

       Each person whose individual signature appears below hereby authorizes
Peter H. van Oppen and Charles H. Stonecipher, or either of them, as
attorneys-in-fact with full power of substitution, to execute in the name and
on the behalf of each person, individually and in each capacity stated below,
and to file, any and all post-effective amendments to this Registration
Statement.

       Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed by the following persons in the
capacities indicated below on the 21st day of December 1999.
SIGNATURE                                 TITLE
/s/ PETER H. VAN OPPEN        Chief Executive Officer and Chairman of
  ---------------------------------   the Board (Principal Executive Officer)
          Peter H. van Oppen

            /s/ JON GACEK             Chief Financial Officer (Principal
  ---------------------------------   Financial and Accounting Officer)
              Jon Gacek

          /s/ TOM A. ALBERG           Director
  ---------------------------------
            Tom A. Alberg

      /s/ CHRISTOPHER T. BAYLEY       Director
  ---------------------------------
        Christopher T. Bayley

        /s/ RUSSELL F. MCNEILL        Director
  ---------------------------------
          Russell F. McNeill

         /s/ JOHN W. STANTON          Director
  ---------------------------------
           John W. Stanton

         /s/ WALTER F. WALKER         Director
  ---------------------------------
           Walter F. Walker
II-4
INDEX TO EXHIBITS
Exhibit
    Number                               Description
------------    ---------------------------------------------------------------
5.1       Opinion of Perkins Coie LLP regarding legality of the Common
                Stock being registered

      23.1      Consent of PricewaterhouseCoopers LLP

      23.2      Consent of Perkins Coie LLP (included in opinion filed as
                Exhibit 5.1)

      24.1      Power of Attorney (see signature page)

      99.1      Advanced Digital Information Corporation 1999 MoutainGate
                Transition Stock Option Plan

      99.2      Advanced Digital Information Corporation 1996 Stock Option Plan