<PAGE>   1
    As filed with the Securities and Exchange Commission on June 25, 1999
                                       Registration No. 333-____________________
--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549



                                    FORM S-8
                             REGISTRATION STATEMENTS
                                      Under
                           The Securities Act of 1933


                        IDEC PHARMACEUTICALS CORPORATION
             (Exact name of registrant as specified in its charter)

            DELAWARE                                     33-0112644
  (State or other jurisdiction                 (IRS Employer Identification No.)
of incorporation or organization)

                              11011 TORREYANA ROAD
                           SAN DIEGO, CALIFORNIA 92121
               (Address of principal executive offices) (Zip Code)



                   AMENDED AND RESTATED 1988 STOCK OPTION PLAN
                        1995 EMPLOYEE STOCK PURCHASE PLAN
                           (Full titles of the Plans)


                           WILLIAM H. RASTETTER, PH.D.
                 CHAIRMAN, PRESIDENT AND CHIEF EXECUTIVE OFFICER
                        IDEC PHARMACEUTICALS CORPORATION
                    11011 TORREYANA ROAD, SAN DIEGO, CA 92121
                     (Name and address of agent for service)
                                 (619) 550-8500
          (Telephone number, including area code, of agent for service)


                         CALCULATION OF REGISTRATION FEE
<TABLE>
<CAPTION>

                                                                         Proposed           Maximum
                                                                          Maximum          Aggregate           Amount of
     Title of Securities to be                      Amount to be      Offering Price       Offering          Registration
            Registered                             Registered(1)       per Share(2)        Price(2)               Fee
=========================================================================================================================
<S>                                               <C>                     <C>            <C>                 <C>
Amended and Restated 1988 Stock Option Plan

Common Stock, $0.001 par value                    800,000 shares          $67.50         $54,000,000.00      $15,012.00

1995 Employee Stock Purchase Plan

Common Stock, $0.001 par value                    200,000 shares          $67.50         $ 3,500,000.00      $ 3,753.00

                                                                                   Aggregate Filing Fee:     $18,765.00
=========================================================================================================================
</TABLE>

(1) This Registration Statement shall also cover any additional shares of Common
    Stock which become issuable under the Amended and Restated 1988 Stock Option
    Plan and/or the 1995 Employee Stock Purchase Plan by reason of any stock
    dividend, stock split, recapitalization or other similar transaction
    effected without the Registrant's receipt of consideration which results in
    an increase in the number of the outstanding shares of Registrant's Common
    Stock.

(2) Calculated solely for purposes of this offering under Rule 457(h) of the
    Securities Act of 1933, as amended, (the "1933 Act") on the basis of the
    average of the high and low selling prices per share of Registrant's Common
    Stock on June 23, 1999 as reported by the Nasdaq National Market.


<PAGE>   2
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT


ITEM 3. INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

        IDEC Pharmaceuticals Corporation (the "Registrant") hereby incorporates
by reference into this Registration Statement the following documents previously
filed with the Securities and Exchange Commission (the "Commission"):

        (a)     The Registrant's Annual Report on Form 10-K for the fiscal year
                ended December 31, 1998 filed with the Commission on March 31,
                1999, pursuant to Section 13 of the Securities Exchange Act of
                1934, as amended (the "Exchange Act");

        (b)     The Registrant's Quarterly Report on Form 10-Q for the fiscal
                quarter ended March 31, 1999 filed with the Commission on May
                17, 1999 pursuant to Section 13 of the Exchange Act;

        (c)     The Registrant's Registration Statement No. 000-13231 on Form
                8-A filed with the Commission on August 1, 1997, in which there
                is described the terms, rights and provisions applicable to the
                Registrant's outstanding Common Stock.

        All reports and definitive proxy or information statements filed
pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date
of this Registration Statement and prior to the filing of a post-effective
amendment which indicates that all securities offered hereby have been sold or
which deregisters all securities then remaining unsold shall be deemed to be
incorporated by reference into this Registration Statement and to be a part
hereof from the date of filing of such documents. Any statement contained in a
document incorporated or deemed to be incorporated by reference herein shall be
deemed to be modified or superseded for purposes of this Registration Statement
to the extent that a statement contained herein or in any subsequently filed
document which is also deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of this
Registration Statement.

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 Registrant'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
for (i) any breach of their duty of loyalty to the corporation or its
stockholders, (ii) any acts or omissions not in good faith or which involve
intentional misconduct or a knowing violation of law, (iii) any unlawful
payments of dividends or unlawful stock repurchases or redemptions as provided
in Section 174 of the Delaware General Corporation Law or (iv) any transaction
from which the director derived an improper personal benefit.


                                      II-1
<PAGE>   3
        The Registrant's Bylaws provide that the Registrant shall indemnify its
directors and may indemnify its officers and employees and other agents to the
fullest extent permitted by law. The Registrant believes that indemnification
under its Bylaws covers at least negligence and gross negligence on the part of
indemnified parties. The Registrant's Bylaws also permit it to secure insurance
on behalf of any officer, director, employee or other agent for any liability
arising out of his or her actions in such capacity, regardless of whether the
Bylaws have the power to indemnify him or her against such liability under the
General Corporation Law of Delaware. The Registrant currently has secured such
insurance on behalf of its directors and officers.

        The Registrant has entered into agreements to indemnify its directors
and executive officers, in addition to indemnification provided for in the
Registrant's Bylaws. These agreements, among other things, indemnify the
Registrant's directors and executive 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 Registrant, arising out of such person's services as a director or executive
officer of the Registrant, any subsidiary of the Registrant or any other company
or enterprise to which the person provides services at the request of the
Registrant. The Registrant believes that these provisions and agreements are
necessary to attract and retain qualified persons as directors and executive
officers.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED

        Not applicable.

ITEM 8. EXHIBITS

EXHIBIT NUMBER            EXHIBIT

        4                 Instruments Defining Rights of Stockholders. Reference
                          is made to Registrant's Registration Statement No.
                          0-19311 on Form 8-B, including exhibits thereto, which
                          is incorporated herein by reference pursuant to Item
                          3(c).

        5                 Opinion of Brobeck, Phleger & Harrison LLP.

        23.1              Consent of Independent Auditors - KPMG LLP.

        23.2              Consent of Brobeck, Phleger & Harrison LLP is
                          contained in Exhibit 5.1.

        24                Power of Attorney. Reference is made to page II-4 of
                          this Registration Statement.

        99.1              Amended and Restated 1988 Stock Option Plan (Amended
                          and Restated May 20, 1999).

        99.2*             Form of Notice of Grant.

        99.3*             Form of Stock Option Agreement.

        99.4              1995 Employee Stock Purchase Plan (Amended and
                          Restated May 20, 1999).

        99.5**            Form of Enrollment/Change Form under 1995 Employee
                          Stock Purchase Plan.

        99.6**            Form of Stock Purchase Agreement under 1995 Employee
                          Stock Purchase Plan.

        *       Exhibits 99.2 and 99.3 are incorporated herein by reference to
                Exhibits 28.2 and 28.3, respectively, of Registrant's
                Registration Statement No. 33-45172 on Form S-8 which was filed
                with the Commission on January 21, 1992.

        **      Exhibits 99.5 and 99.6 are incorporated herein by reference to
                Exhibits 28.2 and 28.3, respectively, of Registrant's
                Registration Statement No. 33-60224 on Form S-8 which was filed
                with the Commission on April 5, 1993.

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 1933 Act, (ii) to reflect in the prospectus any facts
or events arising after the


                                      II-2
<PAGE>   4
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 clauses (1)(i) and (1)(ii) shall 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 into this
Registration Statement; (2) that for the purpose of determining any liability
under the 1933 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; and (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 Registrant's Amended and Restated 1988 Stock
Option Plan and/or 1995 Employee Stock Purchase Plan.

        B.      The undersigned Registrant hereby undertakes that, for purposes
of determining any liability under the 1933 Act, each filing of the Registrant's
annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act
that is incorporated by reference into 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.

        C.      Insofar as indemnification for liabilities arising under the
1933 Act may be permitted to directors, officers or controlling persons of the
Registrant pursuant to the indemnity provisions summarized in Item 6 or
otherwise, the Registrant has been informed that in the opinion of the
Securities and Exchange Commission such indemnification is against public policy
as expressed in the 1933 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 1933 Act
and will be governed by the final adjudication of such issue.


                                      II-3
<PAGE>   5
                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended,
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 Diego, State of California, on this
24th day of June, 1999.

                                       IDEC PHARMACEUTICALS CORPORATION


                                       By /s/ WILLIAM H. RASTETTER
                                       ---------------------------------------
                                       William H. Rastetter
                                       Chairman, President and Chief Executive
                                       Officer


                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

        That the undersigned officers and directors of IDEC Pharmaceuticals
Corporation, a Delaware corporation, do hereby constitute and appoint William H.
Rastetter and Phillip M. Schneider, and each of them, the lawful attorneys and
agents, with full power and authority to do any and all acts and things and to
execute any and all instruments which said attorneys and agents, or any one of
them, determines may be necessary or advisable or required to enable said
corporation to comply with the Securities Act of 1933, as amended, and any rules
or regulations or requirements of the Securities and Exchange Commission in
connection with this Registration Statement. Without limiting the generality of
the foregoing power and authority, the powers granted include the power and
authority to sign the names of the undersigned officers and directors in the
capacities indicated below to this Registration Statement, to any and all
amendments, both pre-effective and post-effective, and supplements to this
Registration Statement, and to any and all instruments or documents filed as
part of or in conjunction with this Registration Statement or amendments or
supplements thereof, and each of the undersigned hereby ratifies and confirms
all that said attorneys and agents, and any one of them, shall do or cause to be
done by virtue hereof. This Power of Attorney may be signed in several
counterparts.

        IN WITNESS WHEREOF, each of the undersigned has executed this Power of
Attorney as of the date indicated.

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

<TABLE>
<CAPTION>
Signatures                     Title                                  Date
----------                     -----                                  ----
<S>                            <C>                                    <C>

/s/ WILLIAM H. RASTETTER
----------------------------   Chairman, President and                June 24, 1999
William H. Rastetter           Chief Executive Officer
                               (Principal Executive Officer)



/s/ PHILLIP M. SCHNEIDER
----------------------------   Vice President and Chief               June 24, 1999
Phillip M. Schneider           Financial Officer (Principal
                               Financial and Accounting Officer)
</TABLE>


                                      II-4
<PAGE>   6
<TABLE>
<CAPTION>
Signatures                     Title                                  Date
----------                     -----                                  ----
<S>                            <C>                                    <C>

/s/ CHARLES C. EDWARDS         Director                               June 25, 1999
-----------------------------
Charles C. Edwards



/s/ ALAN B. GLASSBERG          Director                               June 25, 1999
-----------------------------
Alan B. Glassberg



/s/ KAZUHIRO HASHIMOTO         Director                               June 25, 1999
-----------------------------
Kazuhiro Hashimoto



/s/ FRANKLIN P. JOHNSON, JR.   Director                               June 25, 1999
-----------------------------
Franklin P. Johnson, Jr.



/s/ THE HONORABLE LYNN SCHENK  Director                               June 25, 1999
-----------------------------
The Honorable Lynn Schenk



/s/ WILLIAM D. YOUNG           Director                               June 25, 1999
-----------------------------
William D. Young



                               Director                               June __, 1999
-----------------------------
Robert W. Pangia



/s/ BRUCE R. ROSS              Director                               June 25, 1999
-----------------------------
Bruce R. Ross
</TABLE>


                                      II-5
<PAGE>   7
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    EXHIBITS

                                       TO

                                    FORM S-8

                                      UNDER

                             SECURITIES ACT OF 1933

                        IDEC PHARMACEUTICALS CORPORATION


<PAGE>   8
                                  EXHIBIT INDEX


EXHIBIT NUMBER            EXHIBIT

        4                 Instruments Defining Rights of Stockholders. Reference
                          is made to Registrant's Registration Statement No.
                          0-19311 on Form 8-B, including exhibits thereto, which
                          is incorporated herein by reference pursuant to Item
                          3(c).

        5                 Opinion of Brobeck, Phleger & Harrison LLP.

        23.1              Consent of Independent Auditors - KPMG LLP.

        23.2              Consent of Brobeck, Phleger & Harrison LLP is
                          contained in Exhibit 5.1.

        24                Power of Attorney. Reference is made to page II-4 of
                          this Registration Statement.

        99.1              Amended and Restated 1988 Stock Option Plan (Amended
                          and Restated May 20, 1999).

        99.2*             Form of Notice of Grant.

        99.3*             Form of Stock Option Agreement.

        99.4              1995 Employee Stock Purchase Plan (Amended and
                          Restated May 20, 1999).

        99.5**            Form of Enrollment/Change Form under 1995 Employee
                          Stock Purchase Plan.

        99.6**            Form of Stock Purchase Agreement under 1995 Employee
                          Stock Purchase Plan.

        *       Exhibits 99.2 and 99.3 are incorporated herein by reference to
                Exhibits 28.2 and 28.3, respectively, of Registrant's
                Registration Statement No. 33-45172 on Form S-8 which was filed
                with the Commission on January 21, 1992.

        **      Exhibits 99.5 and 99.6 are incorporated herein by reference to
                Exhibits 28.2 and 28.3, respectively, of Registrant's
                Registration Statement No. 33-60224 on Form S-8 which was filed
                with the Commission on April 5, 1993.
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{"company-data": {"conformed-name": "IDEC PHARMACEUTICALS CORP / DE", "cik": "0000875045", "assigned-sic": "2836", "irs-number": "330112644", "state-of-incorporation": "DE", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-81625", "film-number": "99652866"}, "business-address": {"street1": "11011 TORREYANA ROAD", "city": "SAN DIEGO", "state": "CA", "zip": "92121", "phone": "6195508500"}, "mail-address": {"street1": "11011 TORREYANA ROAD", "city": "SAN DIEGO", "state": "CA", "zip": "92121"}}
1
    As filed with the Securities and Exchange Commission on June 25, 1999
                                       Registration No. 333-____________________
--------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                    FORM S-8
                             REGISTRATION STATEMENTS
                                      Under
                           The Securities Act of 1933

                        IDEC PHARMACEUTICALS CORPORATION
             (Exact name of registrant as specified in its charter)

            DELAWARE                                     33-0112644
  (State or other jurisdiction                 (IRS Employer Identification No.)
of incorporation or organization)

                              11011 TORREYANA ROAD
                           SAN DIEGO, CALIFORNIA 92121
               (Address of principal executive offices) (Zip Code)

                   AMENDED AND RESTATED 1988 STOCK OPTION PLAN
                        1995 EMPLOYEE STOCK PURCHASE PLAN
                           (Full titles of the Plans)

                           WILLIAM H. RASTETTER, PH.D.
                 CHAIRMAN, PRESIDENT AND CHIEF EXECUTIVE OFFICER
                        IDEC PHARMACEUTICALS CORPORATION
                    11011 TORREYANA ROAD, SAN DIEGO, CA 92121
                     (Name and address of agent for service)
                                 (619) 550-8500
          (Telephone number, including area code, of agent for service)

                         CALCULATION OF REGISTRATION FEE
Proposed           Maximum
                                                                          Maximum          Aggregate           Amount of
     Title of Securities to be                      Amount to be      Offering Price       Offering          Registration
            Registered                             Registered(1)       per Share(2)        Price(2)               Fee
=========================================================================================================================
Amended and Restated 1988 Stock Option Plan

Common Stock, $0.001 par value                    800,000 shares          $67.50         $54,000,000.00      $15,012.00

1995 Employee Stock Purchase Plan

Common Stock, $0.001 par value                    200,000 shares          $67.50         $ 3,500,000.00      $ 3,753.00

                                                                                   Aggregate Filing Fee:     $18,765.00
=========================================================================================================================
(1) This Registration Statement shall also cover any additional shares of Common
    Stock which become issuable under the Amended and Restated 1988 Stock Option
    Plan and/or the 1995 Employee Stock Purchase Plan by reason of any stock
    dividend, stock split, recapitalization or other similar transaction
    effected without the Registrant's receipt of consideration which results in
    an increase in the number of the outstanding shares of Registrant's Common
    Stock.

(2) Calculated solely for purposes of this offering under Rule 457(h) of the
    Securities Act of 1933, as amended, (the "1933 Act") on the basis of the
    average of the high and low selling prices per share of Registrant's Common
    Stock on June 23, 1999 as reported by the Nasdaq National Market.
2
                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3. INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

        IDEC Pharmaceuticals Corporation (the "Registrant") hereby incorporates
by reference into this Registration Statement the following documents previously
filed with the Securities and Exchange Commission (the "Commission"):

        (a)     The Registrant's Annual Report on Form 10-K for the fiscal year
                ended December 31, 1998 filed with the Commission on March 31,
                1999, pursuant to Section 13 of the Securities Exchange Act of
                1934, as amended (the "Exchange Act");

        (b)     The Registrant's Quarterly Report on Form 10-Q for the fiscal
                quarter ended March 31, 1999 filed with the Commission on May
                17, 1999 pursuant to Section 13 of the Exchange Act;

        (c)     The Registrant's Registration Statement No. 000-13231 on Form
                8-A filed with the Commission on August 1, 1997, in which there
                is described the terms, rights and provisions applicable to the
                Registrant's outstanding Common Stock.

        All reports and definitive proxy or information statements filed
pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date
of this Registration Statement and prior to the filing of a post-effective
amendment which indicates that all securities offered hereby have been sold or
which deregisters all securities then remaining unsold shall be deemed to be
incorporated by reference into this Registration Statement and to be a part
hereof from the date of filing of such documents. Any statement contained in a
document incorporated or deemed to be incorporated by reference herein shall be
deemed to be modified or superseded for purposes of this Registration Statement
to the extent that a statement contained herein or in any subsequently filed
document which is also deemed to be incorporated by reference herein modifies or
supersedes such statement. Any such statement so modified or superseded shall
not be deemed, except as so modified or superseded, to constitute a part of this
Registration Statement.

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 Registrant'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
for (i) any breach of their duty of loyalty to the corporation or its
stockholders, (ii) any acts or omissions not in good faith or which involve
intentional misconduct or a knowing violation of law, (iii) any unlawful
payments of dividends or unlawful stock repurchases or redemptions as provided
in Section 174 of the Delaware General Corporation Law or (iv) any transaction
from which the director derived an improper personal benefit.

                                      II-1
3
        The Registrant's Bylaws provide that the Registrant shall indemnify its
directors and may indemnify its officers and employees and other agents to the
fullest extent permitted by law. The Registrant believes that indemnification
under its Bylaws covers at least negligence and gross negligence on the part of
indemnified parties. The Registrant's Bylaws also permit it to secure insurance
on behalf of any officer, director, employee or other agent for any liability
arising out of his or her actions in such capacity, regardless of whether the
Bylaws have the power to indemnify him or her against such liability under the
General Corporation Law of Delaware. The Registrant currently has secured such
insurance on behalf of its directors and officers.

        The Registrant has entered into agreements to indemnify its directors
and executive officers, in addition to indemnification provided for in the
Registrant's Bylaws. These agreements, among other things, indemnify the
Registrant's directors and executive 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 Registrant, arising out of such person's services as a director or executive
officer of the Registrant, any subsidiary of the Registrant or any other company
or enterprise to which the person provides services at the request of the
Registrant. The Registrant believes that these provisions and agreements are
necessary to attract and retain qualified persons as directors and executive
officers.

ITEM 7. EXEMPTION FROM REGISTRATION CLAIMED

        Not applicable.

ITEM 8. EXHIBITS

EXHIBIT NUMBER            EXHIBIT

        4                 Instruments Defining Rights of Stockholders. Reference
                          is made to Registrant's Registration Statement No.
                          0-19311 on Form 8-B, including exhibits thereto, which
                          is incorporated herein by reference pursuant to Item
                          3(c).

        5                 Opinion of Brobeck, Phleger & Harrison LLP.

        23.1              Consent of Independent Auditors - KPMG LLP.

        23.2              Consent of Brobeck, Phleger & Harrison LLP is
                          contained in Exhibit 5.1.

        24                Power of Attorney. Reference is made to page II-4 of
                          this Registration Statement.

        99.1              Amended and Restated 1988 Stock Option Plan (Amended
                          and Restated May 20, 1999).

        99.2*             Form of Notice of Grant.

        99.3*             Form of Stock Option Agreement.

        99.4              1995 Employee Stock Purchase Plan (Amended and
                          Restated May 20, 1999).

        99.5**            Form of Enrollment/Change Form under 1995 Employee
                          Stock Purchase Plan.

        99.6**            Form of Stock Purchase Agreement under 1995 Employee
                          Stock Purchase Plan.

        *       Exhibits 99.2 and 99.3 are incorporated herein by reference to
                Exhibits 28.2 and 28.3, respectively, of Registrant's
                Registration Statement No. 33-45172 on Form S-8 which was filed
                with the Commission on January 21, 1992.

        **      Exhibits 99.5 and 99.6 are incorporated herein by reference to
                Exhibits 28.2 and 28.3, respectively, of Registrant's
                Registration Statement No. 33-60224 on Form S-8 which was filed
                with the Commission on April 5, 1993.

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 1933 Act, (ii) to reflect in the prospectus any facts
or events arising after the

                                      II-2
4
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 clauses (1)(i) and (1)(ii) shall 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 into this
Registration Statement; (2) that for the purpose of determining any liability
under the 1933 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; and (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 Registrant's Amended and Restated 1988 Stock
Option Plan and/or 1995 Employee Stock Purchase Plan.

        B.      The undersigned Registrant hereby undertakes that, for purposes
of determining any liability under the 1933 Act, each filing of the Registrant's
annual report pursuant to Section 13(a) or Section 15(d) of the Exchange Act
that is incorporated by reference into 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.

        C.      Insofar as indemnification for liabilities arising under the
1933 Act may be permitted to directors, officers or controlling persons of the
Registrant pursuant to the indemnity provisions summarized in Item 6 or
otherwise, the Registrant has been informed that in the opinion of the
Securities and Exchange Commission such indemnification is against public policy
as expressed in the 1933 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 1933 Act
and will be governed by the final adjudication of such issue.

                                      II-3
5
                                   SIGNATURES

        Pursuant to the requirements of the Securities Act of 1933, as amended,
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 Diego, State of California, on this
24th day of June, 1999.

                                       IDEC PHARMACEUTICALS CORPORATION

                                       By /s/ WILLIAM H. RASTETTER
                                       ---------------------------------------
                                       William H. Rastetter
                                       Chairman, President and Chief Executive
                                       Officer

                                POWER OF ATTORNEY

KNOW ALL MEN BY THESE PRESENTS:

        That the undersigned officers and directors of IDEC Pharmaceuticals
Corporation, a Delaware corporation, do hereby constitute and appoint William H.
Rastetter and Phillip M. Schneider, and each of them, the lawful attorneys and
agents, with full power and authority to do any and all acts and things and to
execute any and all instruments which said attorneys and agents, or any one of
them, determines may be necessary or advisable or required to enable said
corporation to comply with the Securities Act of 1933, as amended, and any rules
or regulations or requirements of the Securities and Exchange Commission in
connection with this Registration Statement. Without limiting the generality of
the foregoing power and authority, the powers granted include the power and
authority to sign the names of the undersigned officers and directors in the
capacities indicated below to this Registration Statement, to any and all
amendments, both pre-effective and post-effective, and supplements to this
Registration Statement, and to any and all instruments or documents filed as
part of or in conjunction with this Registration Statement or amendments or
supplements thereof, and each of the undersigned hereby ratifies and confirms
all that said attorneys and agents, and any one of them, shall do or cause to be
done by virtue hereof. This Power of Attorney may be signed in several
counterparts.

        IN WITNESS WHEREOF, each of the undersigned has executed this Power of
Attorney as of the date indicated.

        Pursuant to the requirements of the Securities Act of 1933, as amended,
this Registration Statement has been signed below by the following persons in
the capacities and on the dates indicated.
Signatures                     Title                                  Date
----------                     -----                                  ----
/s/ WILLIAM H. RASTETTER
----------------------------   Chairman, President and                June 24, 1999
William H. Rastetter           Chief Executive Officer
                               (Principal Executive Officer)

/s/ PHILLIP M. SCHNEIDER
----------------------------   Vice President and Chief               June 24, 1999
Phillip M. Schneider           Financial Officer (Principal
                               Financial and Accounting Officer)
II-4
6
Signatures                     Title                                  Date
----------                     -----                                  ----
/s/ CHARLES C. EDWARDS         Director                               June 25, 1999
-----------------------------
Charles C. Edwards

/s/ ALAN B. GLASSBERG          Director                               June 25, 1999
-----------------------------
Alan B. Glassberg

/s/ KAZUHIRO HASHIMOTO         Director                               June 25, 1999
-----------------------------
Kazuhiro Hashimoto

/s/ FRANKLIN P. JOHNSON, JR.   Director                               June 25, 1999
-----------------------------
Franklin P. Johnson, Jr.

/s/ THE HONORABLE LYNN SCHENK  Director                               June 25, 1999
-----------------------------
The Honorable Lynn Schenk

/s/ WILLIAM D. YOUNG           Director                               June 25, 1999
-----------------------------
William D. Young

                               Director                               June __, 1999
-----------------------------
Robert W. Pangia

/s/ BRUCE R. ROSS              Director                               June 25, 1999
-----------------------------
Bruce R. Ross
II-5
7
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                    EXHIBITS

                                       TO

                                    FORM S-8

                                      UNDER

                             SECURITIES ACT OF 1933

                        IDEC PHARMACEUTICALS CORPORATION
8
                                  EXHIBIT INDEX

EXHIBIT NUMBER            EXHIBIT

        4                 Instruments Defining Rights of Stockholders. Reference
                          is made to Registrant's Registration Statement No.
                          0-19311 on Form 8-B, including exhibits thereto, which
                          is incorporated herein by reference pursuant to Item
                          3(c).

        5                 Opinion of Brobeck, Phleger & Harrison LLP.

        23.1              Consent of Independent Auditors - KPMG LLP.

        23.2              Consent of Brobeck, Phleger & Harrison LLP is
                          contained in Exhibit 5.1.

        24                Power of Attorney. Reference is made to page II-4 of
                          this Registration Statement.

        99.1              Amended and Restated 1988 Stock Option Plan (Amended
                          and Restated May 20, 1999).

        99.2*             Form of Notice of Grant.

        99.3*             Form of Stock Option Agreement.

        99.4              1995 Employee Stock Purchase Plan (Amended and
                          Restated May 20, 1999).

        99.5**            Form of Enrollment/Change Form under 1995 Employee
                          Stock Purchase Plan.

        99.6**            Form of Stock Purchase Agreement under 1995 Employee
                          Stock Purchase Plan.

        *       Exhibits 99.2 and 99.3 are incorporated herein by reference to
                Exhibits 28.2 and 28.3, respectively, of Registrant's
                Registration Statement No. 33-45172 on Form S-8 which was filed
                with the Commission on January 21, 1992.

        **      Exhibits 99.5 and 99.6 are incorporated herein by reference to
                Exhibits 28.2 and 28.3, respectively, of Registrant's
                Registration Statement No. 33-60224 on Form S-8 which was filed
                with the Commission on April 5, 1993.