<PAGE>   1

     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON APRIL 10, 2001
                                                           REGISTRATION NO. 333-

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


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

                          ARONEX PHARMACEUTICALS, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

                      DELAWARE                                76-0196535
          (STATE OR OTHER JURISDICTION OF                  (I.R.S. EMPLOYER
           INCORPORATION OR ORGANIZATION)                 IDENTIFICATION NO.)

            8707 TECHNOLOGY FOREST PLACE
                THE WOODLANDS, TEXAS                          77381-1191
      (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)                (ZIP CODE)

                     1998 STOCK OPTION PLAN, AS AMENDED AND
    AMENDED AND RESTATED 1993 NON-EMPLOYEE DIRECTORS' OPTION PLAN, AS AMENDED
                           (FULL TITLES OF THE PLANS)

                             GEOFFREY F. COX, PH.D.
                CHAIRMAN OF THE BOARD AND CHIEF EXECUTIVE OFFICER
                          ARONEX PHARMACEUTICALS, INC.
                          8707 TECHNOLOGY FOREST PLACE
                         THE WOODLANDS, TEXAS 77381-1191
                     (NAME AND ADDRESS OF AGENT FOR SERVICE)
                                 (281) 367-1666
          (TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                                    COPY TO:
                                JEFFREY R. HARDER
                             ANDREWS & KURTH L.L.P.
                        2170 BUCKTHORNE PLACE, SUITE 150
                           THE WOODLANDS, TEXAS 77380
                                 (713) 220-4801

                         CALCULATION OF REGISTRATION FEE

<TABLE>
<CAPTION>
====================================================================================================================
                                                                                        PROPOSED
                                                                        PROPOSED         MAXIMUM
                                                                         MAXIMUM        AGGREGATE         AMOUNT OF
  TITLE OF SECURITIES                                AMOUNT TO BE     OFFERING PRICE     OFFERING       REGISTRATION
    TO BE REGISTERED       TITLE OF PLANS            REGISTERED(1)     PER SHARE(2)      PRICE(2)            FEE
--------------------------------------------------------------------------------------------------------------------

<S>                     <C>                       <C>                 <C>              <C>              <C>
   Common Stock, par    Amended and Restated       1,900,000 shares      $0.5625        $1,068,750         $267.19
    value $.001 per     1998 Stock Option Plan
     share ("Common
        Stock")
--------------------------------------------------------------------------------------------------------------------
     Common Stock       Amended and Restated         600,000 shares      $0.5625        $  337,500         $ 84.38
                        1993 Non-Employee
                        Directors' Option Plan
====================================================================================================================
</TABLE>

(1)      Pursuant to Rule 416(a), this registration statement shall cover any
         additional securities issued to prevent dilution resulting from stock
         splits, stock dividends or similar transactions.

(2)      Estimated solely for the purpose of calculating the registration fee
         pursuant to Rule 457 (c) and (h), based on the average of the high and
         low sales price per share of the registrant's common stock, as reported
         on The Nasdaq Stock Market on April 4, 2001.


<PAGE>   2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         Aronex Pharmaceuticals, Inc. (the "Company") incorporates herein by
reference the following documents, as filed with the Securities and Exchange
Commission (the "Commission"), as of their respective filing dates:

                    (a) The Company's Annual Report on Form 10-K (File No.
               0-21198) for the year ended December 31, 2000;

                    (b) The description of the Company's common stock, par value
               $0.001 per share, contained in the Company's registration
               statement on Form 8-A filed with the Commission on April 23,
               1992, including any amendments and reports filed for the purpose
               of updating such description.

         All documents filed by the Company pursuant to Section 13(a), 13(c), 14
and 15(d) of the Securities Exchange Act of 1934, as amended (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 such securities then remaining unsold
shall be deemed to be incorporated by reference in this registration statement
and to be a part hereof from the date of filing such documents.

ITEM 4.  DESCRIPTION OF SECURITIES.

         The information required by Item 4 is not applicable to this
registration statement because the class of securities to be offered is
registered under Section 12 of the Exchange Act.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

         The information required by Item 5 is not applicable to this
registration statement.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Section 145 of the Delaware General Corporation Law ("DGCL"), inter
alia, empowers a Delaware corporation to indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding (other than an action by or in the right of
the corporation) by reason of the fact that such person is or was a director,
officer, employee or agent of the corporation, or is or was serving at the
request of the corporation as a director, officer, employee or agent of another
corporation or other enterprise, against expenses (including attorneys' fees),
judgments, fines and amounts paid in settlement actually and reasonably incurred
by him in connection with such action, suit or proceeding if he acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests of the corporation, and, with respect to any criminal action or
proceeding, had no reasonable cause to believe his conduct was unlawful. Similar
indemnity is authorized for such persons against expenses (including attorneys'
fees) actually and reasonably incurred in connection with the defense or
settlement of any such threatened, pending or completed action or suit if such
person acted in good faith and in a manner he reasonably believed to be in or
not opposed to the best interests of the corporation, and provided further that
(unless a court of competent jurisdiction otherwise provides) such person shall
not have been adjudged liable to the corporation. Any such indemnification may
be made only as authorized in each specific case upon a determination by the
stockholders or disinterested directors or by independent legal counsel in a
written opinion that indemnification is proper because the indemnitee has met
the applicable standard of conduct.

         Section 145 further authorizes a corporation to purchase and maintain
insurance on behalf of any person who is or was a director, officer, employee or
agent of the corporation, or is or was serving at the request of the corporation
as a director, officer, employee or agent of another corporation or enterprise,
against any liability asserted against him and incurred by him in any such
capacity, or arising out of his status as such, whether or not the corporation
would otherwise have the power to indemnify him under Section 145. The Company
maintains policies



                                      II-1
<PAGE>   3

insuring its and its subsidiaries' officers and directors against certain
liabilities for actions taken in such capacities, including liabilities under
the Securities Act of 1933, as amended (the "Securities Act").

         Article VII of the Company's Amended and Restated Certificate of
Incorporation, as amended (the "Charter"), limits under certain circumstances
the liability of the Company's directors for a breach of their fiduciary duty as
directors. These provisions do not eliminate the liability of a director (i) for
a breach of the director's duty of loyalty to the Company or its stockholders,
(ii) for acts or omissions not in good faith or that involve intentional
misconduct or a knowing violation of law, (iii) under Section 174 of the DGCL
(relating to the declaration of dividends and purchase or redemption of shares
in violation of the DGCL) or (iv) for any transaction from which the director
derived an improper personal benefit.

         Article VIII of the Company's Charter and Article VII of the Company's
Restated Bylaws provide for indemnification of the directors, officers and
employees of the Company to the fullest extent permitted by law. The Company
currently has a liability insurance policy which insures directors and officers
of the Company in certain circumstances. The policy also insures the Company
against losses as to which its directors and officers are entitled to
indemnification.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable.

ITEM 8.  EXHIBITS.

    Exhibit
    Number       Description

    3.1(a)+      Restated Certificate of Incorporation (incorporated by
                 reference to Exhibit 3.1 to the Company's Quarterly Report on
                 Form 10-Q for the fiscal quarter ended June 30, 1997).

    3.1(b)+      Certificate of Amendment of Amended and Restated Certificate of
                 Incorporation (incorporated by reference to Exhibit 3.1(i) to
                 the Company's Quarterly Report on Form 10-Q for the fiscal
                 quarter ended June 30, 1999).

    3.1(c)+      Certificate of Designation of Series One Junior Participating
                 Preferred Stock dated October 6, 1999 (incorporated by
                 reference to Exhibit A to Exhibit 4.1 on the Company's
                 Registration Statement on Form 8-A dated October 7, 1999).

    3.2+         Restated Bylaws (incorporated by reference to Exhibit 3.2 to
                 the Company's Registration Statement on Form S-1 (No.
                 33-47418), declared effective by the Commission on July 10,
                 1992).

    3.3+         Specimen Common Stock Certificate (incorporated by reference
                 to Exhibit 4.1 to the Company's Quarterly Report on Form 10-Q
                 for the fiscal quarter ended June 30, 1996).

    5.1*         Opinion of Andrews & Kurth L.L.P.

    23.1*        Consent of Andrews & Kurth L.L.P. (included in Exhibit 5.1).

    23.2*        Consent of Arthur Andersen LLP

    24.1*        Power of Attorney (set forth on the signature page contained
                 in Part II of this Registration Statement).

    99.1*        1998 Stock Option Plan, as amended.

    99.2*        Non-Employee Director Stock Option Plan, as amended.

+ Incorporated herein by reference.
* Filed herewith.



                                      II-2
<PAGE>   4

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;

                         (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 (a)(1)(i) and (a)(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 Company pursuant to Section 13 or
               Section 15(d) of the Exchange Act that are incorporated by
               reference 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 Exchange Act, each filing of the Company's
annual report pursuant to Section 13(a) or 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.

         (c) Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Company pursuant to the foregoing provisions, or otherwise, the Company
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 Company of expenses incurred or paid
by a director, officer or controlling person of the Company 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
Company 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>   5

                                   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 Woodlands, Texas, on the 10th day of April, 2001.

                                   ARONEX PHARMACEUTICALS, INC.


                                   By: /s/ Geoffrey F. Cox, Ph.D.
                                      ------------------------------------------
                                      Geoffrey F. Cox, Ph.D.
                                      Chairman of the Board and Chief Executive
                                      Officer

                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS, that each of the undersigned officers
and directors of Aronex Pharmaceuticals, Inc. (the "Company") hereby constitutes
and appoints Geoffrey F. Cox, Ph.D. and Terance A. Murnane, and each of them
(with full power to each of them to act alone), his true and lawful
attorney-in-fact and agent, with full power of substitution, for him and on his
behalf and in his name, place and stead, in any and all capacities, to sign,
execute and file this registration statement under the Securities Act of 1933,
as amended, and any or all amendments (including, without limitation,
post-effective amendments), with all exhibits and any and all documents required
to be filed with respect thereto, with the Securities and Exchange Commission or
any regulatory authority, granting unto such attorneys-in-fact and agents, and
each of them, full power and authority to do and perform each and every act and
thing requisite and necessary to be done in order to effectuate the same, as
fully to all intents and purposes as he himself might or could do if personally
present, hereby ratifying and confirming all that such attorneys-in-fact and
agents, or any of them, or their substitute or substitutes, may lawfully do or
cause to be done.

         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 DATES INDICATED.

<TABLE>
<CAPTION>
                SIGNATURE                                     TITLE                                 DATE
                ---------                                     -----                                 ----
<S>                                        <C>                                                 <C>
/s/      Geoffrey F. Cox, Ph.D.                     Chairman of the Board and                  April 10, 2001
--------------------------------------                Chief Executive Officer
         Geoffrey F. Cox, Ph.D.                   (Principal Executive Officer)

/s/      Terance A. Murnane                                 Controller                         April 10, 2001
--------------------------------------     (Principal Financial and Accounting Officer)
         Terance A. Murnane

/s/      James R. Butler                                     Director                          April 10, 2001
--------------------------------------
         James R. Butler

/s/      Gabriel Lopez-Berestein, M.D.                       Director                          April 10, 2001
--------------------------------------
         Gabriel Lopez-Berestein, M.D.

/s/      Phyllis I. Gardner, M.D.                            Director                          April 10, 2001
--------------------------------------
         Phyllis I. Gardner, M.D.

/s/      Martin P. Sutter                                    Director                          April 10, 2001
--------------------------------------
         Martin P. Sutter

/s/      Gregory F. Zaic                                     Director                          April 10, 2001
--------------------------------------
         Gregory F. Zaic

/s/      David J. McLachlan                                  Director                          April 10, 2001
--------------------------------------
         David J. McLachlan

/s/      Paul W. Hobby                                       Director                          April 10, 2001
--------------------------------------
         Paul W. Hobby
</TABLE>



                                      II-4
<PAGE>   6


                               INDEX TO EXHIBITS

<TABLE>
<CAPTION>
     EXHIBIT
     NUMBER       DESCRIPTION
     -------      -----------
<S>               <C>

     3.1(a)+      Restated Certificate of Incorporation (incorporated by
                  reference to Exhibit 3.1 to the Company's Quarterly Report on
                  Form 10-Q for the fiscal quarter ended June 30, 1997).

     3.1(b)+      Certificate of Amendment of Amended and Restated Certificate
                  of Incorporation (incorporated by reference to Exhibit 3.1(i)
                  to the Company's Quarterly Report on Form 10-Q for the fiscal
                  quarter ended June 30, 1999).

     3.1(c)+      Certificate of Designation of Series One Junior Participating
                  Preferred Stock dated October 6, 1999 (incorporated by
                  reference to Exhibit A to Exhibit 4.1 on the Company's
                  Registration Statement on Form 8-A dated October 7, 1999).

     3.2+         Restated Bylaws (incorporated by reference to Exhibit 3.2 to
                  the Company's Registration Statement on Form S-1 (No.
                  33-47418), declared effective by the Commission on July 10,
                  1992).

     3.3+         Specimen Common Stock Certificate (incorporated by reference
                  to Exhibit 4.1 to the Company's Quarterly Report on Form 10-Q
                  for the fiscal quarter ended June 30, 1996).

     5.1*         Opinion of Andrews & Kurth L.L.P.

     23.1*        Consent of Andrews & Kurth L.L.P. (included in Exhibit 5.1).

     23.2*        Consent of Arthur Andersen LLP.

     24.1*        Power of Attorney (set forth on the signature page contained
                  in Part II of this Registration Statement).

     99.1*        1998 Stock Option Plan, as amended.

     99.2*        Non-Employee Director Stock Option Plan, as amended.

</TABLE>

+ Incorporated herein by reference.
* Filed herewith.




                                      II-5
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1

     AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON APRIL 10, 2001
                                                           REGISTRATION NO. 333-

================================================================================

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

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

                          ARONEX PHARMACEUTICALS, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

                      DELAWARE                                76-0196535
          (STATE OR OTHER JURISDICTION OF                  (I.R.S. EMPLOYER
           INCORPORATION OR ORGANIZATION)                 IDENTIFICATION NO.)

            8707 TECHNOLOGY FOREST PLACE
                THE WOODLANDS, TEXAS                          77381-1191
      (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)                (ZIP CODE)

                     1998 STOCK OPTION PLAN, AS AMENDED AND
    AMENDED AND RESTATED 1993 NON-EMPLOYEE DIRECTORS' OPTION PLAN, AS AMENDED
                           (FULL TITLES OF THE PLANS)

                             GEOFFREY F. COX, PH.D.
                CHAIRMAN OF THE BOARD AND CHIEF EXECUTIVE OFFICER
                          ARONEX PHARMACEUTICALS, INC.
                          8707 TECHNOLOGY FOREST PLACE
                         THE WOODLANDS, TEXAS 77381-1191
                     (NAME AND ADDRESS OF AGENT FOR SERVICE)
                                 (281) 367-1666
          (TELEPHONE NUMBER, INCLUDING AREA CODE, OF AGENT FOR SERVICE)

                                    COPY TO:
                                JEFFREY R. HARDER
                             ANDREWS & KURTH L.L.P.
                        2170 BUCKTHORNE PLACE, SUITE 150
                           THE WOODLANDS, TEXAS 77380
                                 (713) 220-4801

                         CALCULATION OF REGISTRATION FEE
====================================================================================================================
                                                                                        PROPOSED
                                                                        PROPOSED         MAXIMUM
                                                                         MAXIMUM        AGGREGATE         AMOUNT OF
  TITLE OF SECURITIES                                AMOUNT TO BE     OFFERING PRICE     OFFERING       REGISTRATION
    TO BE REGISTERED       TITLE OF PLANS            REGISTERED(1)     PER SHARE(2)      PRICE(2)            FEE
--------------------------------------------------------------------------------------------------------------------
Common Stock, par    Amended and Restated       1,900,000 shares      $0.5625        $1,068,750         $267.19
    value $.001 per     1998 Stock Option Plan
     share ("Common
        Stock")
--------------------------------------------------------------------------------------------------------------------
     Common Stock       Amended and Restated         600,000 shares      $0.5625        $  337,500         $ 84.38
                        1993 Non-Employee
                        Directors' Option Plan
====================================================================================================================
(1)      Pursuant to Rule 416(a), this registration statement shall cover any
         additional securities issued to prevent dilution resulting from stock
         splits, stock dividends or similar transactions.

(2)      Estimated solely for the purpose of calculating the registration fee
         pursuant to Rule 457 (c) and (h), based on the average of the high and
         low sales price per share of the registrant's common stock, as reported
         on The Nasdaq Stock Market on April 4, 2001.
2

                                     PART II

               INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

ITEM 3.  INCORPORATION OF DOCUMENTS BY REFERENCE.

         Aronex Pharmaceuticals, Inc. (the "Company") incorporates herein by
reference the following documents, as filed with the Securities and Exchange
Commission (the "Commission"), as of their respective filing dates:

                    (a) The Company's Annual Report on Form 10-K (File No.
               0-21198) for the year ended December 31, 2000;

                    (b) The description of the Company's common stock, par value
               $0.001 per share, contained in the Company's registration
               statement on Form 8-A filed with the Commission on April 23,
               1992, including any amendments and reports filed for the purpose
               of updating such description.

         All documents filed by the Company pursuant to Section 13(a), 13(c), 14
and 15(d) of the Securities Exchange Act of 1934, as amended (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 such securities then remaining unsold
shall be deemed to be incorporated by reference in this registration statement
and to be a part hereof from the date of filing such documents.

ITEM 4.  DESCRIPTION OF SECURITIES.

         The information required by Item 4 is not applicable to this
registration statement because the class of securities to be offered is
registered under Section 12 of the Exchange Act.

ITEM 5.  INTERESTS OF NAMED EXPERTS AND COUNSEL.

         The information required by Item 5 is not applicable to this
registration statement.

ITEM 6.  INDEMNIFICATION OF DIRECTORS AND OFFICERS.

         Section 145 of the Delaware General Corporation Law ("DGCL"), inter
alia, empowers a Delaware corporation to indemnify any person who was or is a
party or is threatened to be made a party to any threatened, pending or
completed action, suit or proceeding (other than an action by or in the right of
the corporation) by reason of the fact that such person is or was a director,
officer, employee or agent of the corporation, or is or was serving at the
request of the corporation as a director, officer, employee or agent of another
corporation or other enterprise, against expenses (including attorneys' fees),
judgments, fines and amounts paid in settlement actually and reasonably incurred
by him in connection with such action, suit or proceeding if he acted in good
faith and in a manner he reasonably believed to be in or not opposed to the best
interests of the corporation, and, with respect to any criminal action or
proceeding, had no reasonable cause to believe his conduct was unlawful. Similar
indemnity is authorized for such persons against expenses (including attorneys'
fees) actually and reasonably incurred in connection with the defense or
settlement of any such threatened, pending or completed action or suit if such
person acted in good faith and in a manner he reasonably believed to be in or
not opposed to the best interests of the corporation, and provided further that
(unless a court of competent jurisdiction otherwise provides) such person shall
not have been adjudged liable to the corporation. Any such indemnification may
be made only as authorized in each specific case upon a determination by the
stockholders or disinterested directors or by independent legal counsel in a
written opinion that indemnification is proper because the indemnitee has met
the applicable standard of conduct.

         Section 145 further authorizes a corporation to purchase and maintain
insurance on behalf of any person who is or was a director, officer, employee or
agent of the corporation, or is or was serving at the request of the corporation
as a director, officer, employee or agent of another corporation or enterprise,
against any liability asserted against him and incurred by him in any such
capacity, or arising out of his status as such, whether or not the corporation
would otherwise have the power to indemnify him under Section 145. The Company
maintains policies

                                      II-1
3

insuring its and its subsidiaries' officers and directors against certain
liabilities for actions taken in such capacities, including liabilities under
the Securities Act of 1933, as amended (the "Securities Act").

         Article VII of the Company's Amended and Restated Certificate of
Incorporation, as amended (the "Charter"), limits under certain circumstances
the liability of the Company's directors for a breach of their fiduciary duty as
directors. These provisions do not eliminate the liability of a director (i) for
a breach of the director's duty of loyalty to the Company or its stockholders,
(ii) for acts or omissions not in good faith or that involve intentional
misconduct or a knowing violation of law, (iii) under Section 174 of the DGCL
(relating to the declaration of dividends and purchase or redemption of shares
in violation of the DGCL) or (iv) for any transaction from which the director
derived an improper personal benefit.

         Article VIII of the Company's Charter and Article VII of the Company's
Restated Bylaws provide for indemnification of the directors, officers and
employees of the Company to the fullest extent permitted by law. The Company
currently has a liability insurance policy which insures directors and officers
of the Company in certain circumstances. The policy also insures the Company
against losses as to which its directors and officers are entitled to
indemnification.

ITEM 7.  EXEMPTION FROM REGISTRATION CLAIMED.

         Not applicable.

ITEM 8.  EXHIBITS.

    Exhibit
    Number       Description

    3.1(a)+      Restated Certificate of Incorporation (incorporated by
                 reference to Exhibit 3.1 to the Company's Quarterly Report on
                 Form 10-Q for the fiscal quarter ended June 30, 1997).

    3.1(b)+      Certificate of Amendment of Amended and Restated Certificate of
                 Incorporation (incorporated by reference to Exhibit 3.1(i) to
                 the Company's Quarterly Report on Form 10-Q for the fiscal
                 quarter ended June 30, 1999).

    3.1(c)+      Certificate of Designation of Series One Junior Participating
                 Preferred Stock dated October 6, 1999 (incorporated by
                 reference to Exhibit A to Exhibit 4.1 on the Company's
                 Registration Statement on Form 8-A dated October 7, 1999).

    3.2+         Restated Bylaws (incorporated by reference to Exhibit 3.2 to
                 the Company's Registration Statement on Form S-1 (No.
                 33-47418), declared effective by the Commission on July 10,
                 1992).

    3.3+         Specimen Common Stock Certificate (incorporated by reference
                 to Exhibit 4.1 to the Company's Quarterly Report on Form 10-Q
                 for the fiscal quarter ended June 30, 1996).

    5.1*         Opinion of Andrews & Kurth L.L.P.

    23.1*        Consent of Andrews & Kurth L.L.P. (included in Exhibit 5.1).

    23.2*        Consent of Arthur Andersen LLP

    24.1*        Power of Attorney (set forth on the signature page contained
                 in Part II of this Registration Statement).

    99.1*        1998 Stock Option Plan, as amended.

    99.2*        Non-Employee Director Stock Option Plan, as amended.

+ Incorporated herein by reference.
* Filed herewith.

                                      II-2
4

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;

                         (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 (a)(1)(i) and (a)(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 Company pursuant to Section 13 or
               Section 15(d) of the Exchange Act that are incorporated by
               reference 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 Exchange Act, each filing of the Company's
annual report pursuant to Section 13(a) or 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.

         (c) Insofar as indemnification for liabilities arising under the
Securities Act may be permitted to directors, officers and controlling persons
of the Company pursuant to the foregoing provisions, or otherwise, the Company
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 Company of expenses incurred or paid
by a director, officer or controlling person of the Company 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
Company 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
5

                                   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 Woodlands, Texas, on the 10th day of April, 2001.

                                   ARONEX PHARMACEUTICALS, INC.

                                   By: /s/ Geoffrey F. Cox, Ph.D.
                                      ------------------------------------------
                                      Geoffrey F. Cox, Ph.D.
                                      Chairman of the Board and Chief Executive
                                      Officer

                                POWER OF ATTORNEY

         KNOW ALL MEN BY THESE PRESENTS, that each of the undersigned officers
and directors of Aronex Pharmaceuticals, Inc. (the "Company") hereby constitutes
and appoints Geoffrey F. Cox, Ph.D. and Terance A. Murnane, and each of them
(with full power to each of them to act alone), his true and lawful
attorney-in-fact and agent, with full power of substitution, for him and on his
behalf and in his name, place and stead, in any and all capacities, to sign,
execute and file this registration statement under the Securities Act of 1933,
as amended, and any or all amendments (including, without limitation,
post-effective amendments), with all exhibits and any and all documents required
to be filed with respect thereto, with the Securities and Exchange Commission or
any regulatory authority, granting unto such attorneys-in-fact and agents, and
each of them, full power and authority to do and perform each and every act and
thing requisite and necessary to be done in order to effectuate the same, as
fully to all intents and purposes as he himself might or could do if personally
present, hereby ratifying and confirming all that such attorneys-in-fact and
agents, or any of them, or their substitute or substitutes, may lawfully do or
cause to be done.

         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 DATES INDICATED.
SIGNATURE                                     TITLE                                 DATE
                ---------                                     -----                                 ----
/s/      Geoffrey F. Cox, Ph.D.                     Chairman of the Board and                  April 10, 2001
--------------------------------------                Chief Executive Officer
         Geoffrey F. Cox, Ph.D.                   (Principal Executive Officer)

/s/      Terance A. Murnane                                 Controller                         April 10, 2001
--------------------------------------     (Principal Financial and Accounting Officer)
         Terance A. Murnane

/s/      James R. Butler                                     Director                          April 10, 2001
--------------------------------------
         James R. Butler

/s/      Gabriel Lopez-Berestein, M.D.                       Director                          April 10, 2001
--------------------------------------
         Gabriel Lopez-Berestein, M.D.

/s/      Phyllis I. Gardner, M.D.                            Director                          April 10, 2001
--------------------------------------
         Phyllis I. Gardner, M.D.

/s/      Martin P. Sutter                                    Director                          April 10, 2001
--------------------------------------
         Martin P. Sutter

/s/      Gregory F. Zaic                                     Director                          April 10, 2001
--------------------------------------
         Gregory F. Zaic

/s/      David J. McLachlan                                  Director                          April 10, 2001
--------------------------------------
         David J. McLachlan

/s/      Paul W. Hobby                                       Director                          April 10, 2001
--------------------------------------
         Paul W. Hobby
II-4
6

                               INDEX TO EXHIBITS
EXHIBIT
     NUMBER       DESCRIPTION
     -------      -----------
3.1(a)+      Restated Certificate of Incorporation (incorporated by
                  reference to Exhibit 3.1 to the Company's Quarterly Report on
                  Form 10-Q for the fiscal quarter ended June 30, 1997).

     3.1(b)+      Certificate of Amendment of Amended and Restated Certificate
                  of Incorporation (incorporated by reference to Exhibit 3.1(i)
                  to the Company's Quarterly Report on Form 10-Q for the fiscal
                  quarter ended June 30, 1999).

     3.1(c)+      Certificate of Designation of Series One Junior Participating
                  Preferred Stock dated October 6, 1999 (incorporated by
                  reference to Exhibit A to Exhibit 4.1 on the Company's
                  Registration Statement on Form 8-A dated October 7, 1999).

     3.2+         Restated Bylaws (incorporated by reference to Exhibit 3.2 to
                  the Company's Registration Statement on Form S-1 (No.
                  33-47418), declared effective by the Commission on July 10,
                  1992).

     3.3+         Specimen Common Stock Certificate (incorporated by reference
                  to Exhibit 4.1 to the Company's Quarterly Report on Form 10-Q
                  for the fiscal quarter ended June 30, 1996).

     5.1*         Opinion of Andrews & Kurth L.L.P.

     23.1*        Consent of Andrews & Kurth L.L.P. (included in Exhibit 5.1).

     23.2*        Consent of Arthur Andersen LLP.

     24.1*        Power of Attorney (set forth on the signature page contained
                  in Part II of this Registration Statement).

     99.1*        1998 Stock Option Plan, as amended.

     99.2*        Non-Employee Director Stock Option Plan, as amended.
+ Incorporated herein by reference.
* Filed herewith.

                                      II-5