<PAGE>

                                                                    Exhibit 14.1

                               ILEX ONCOLOGY, INC.

                                 CODE OF ETHICS

                          FOR SENIOR FINANCIAL OFFICERS

I.       PREFACE

         The Board of Directors ("Board") of ILEX Oncology, Inc. (the "Company")
has adopted this Code of Ethics for Senior Financial Officers ("Code") of the
Company. This Code shall be applicable to the Company's chief executive officer,
chief financial officer, treasurer, senior director of accounting, senior
directors of finance, director of finance, associate director for treasury/risk
management and any other employees of the Company performing similar functions
(the "Senior Financial Officers").

II.      PURPOSE

         The purpose of this Code is to codify those standards that the Company
believes are reasonably designed to deter wrong-doing and to promote, on the
part of the Senior Financial Officers, adherence to the following principles in
all material respects:

              -   Honest and ethical conduct, including the ethical handling of
                  actual or apparent conflicts of interest between personal and
                  professional relationships;

              -   Full, fair, accurate, timely and understandable disclosure in
                  reports and documents that the Company files with, or submits
                  to, the Securities and Exchange Commission (the "SEC") and in
                  other public communications made by the Company;

              -   The prompt internal reporting to an appropriate person or
                  persons identified in this Code of violations of this Code;
                  and

              -   Accountability for adherence to this Code.

         No provision of this Code, however, is intended to create any right in
favor of any third party, including any stockholder, officer, director or
employee of the Company, in the event of a violation of any provision of this
Code.

III.     HONEST AND ETHICAL CONDUCT AND ETHICAL HANDLING OF CONFLICTS OF
         INTEREST

         The Senior Financial Officers should conduct themselves and their
activities on behalf of the Company, its subsidiaries and affiliated entities in
an honest and ethical manner and in a

<PAGE>

manner that complies with this Code.

         The Senior Financial Officers should endeavor to avoid any actual or
potential conflict of interest between their personal and professional
relationships. The Senior Financial Officers should promptly disclose all
material facts relating to their relationships or financial interests which give
rise, directly or indirectly, to an actual or potential conflict of interest in
a report to the Audit Committee of the Board. No Senior Financial Officer should
knowingly become involved in any actual or potential conflict of interest
without the relationship or financial interest having been approved by the Board
or the Audit Committee thereof.

IV.      DISCLOSURE IN SEC FILINGS AND OTHER PUBLIC COMMUNICATIONS

         The Senior Financial Officers should conduct themselves and their
activities on behalf of the Company, its subsidiaries and affiliated entities in
a manner which promotes the full, fair, accurate, timely and understandable
disclosure, in accordance with applicable laws, rules or regulations, of all
material information required to be included in (i) each report or other
document required to be filed or submitted by the Company with the SEC and (ii)
in all other public communications made by the Company. To this end, the Senior
Financial Officers should oversee the establishment and management of the
Company's internal controls and disclosure controls and procedures to enable:

              -   The Company's consolidated financial statements and the notes
                  thereto to present fairly, in all material respects, the
                  financial position, the results of operations and the cash
                  flows of the Company as of and for the period(s) indicated in
                  conformity with accounting principles generally accepted in
                  the United States; and

              -   The Senior Financial Officers are to bring to the attention of
                  the Audit Committee of the Board any information, of which
                  they are aware, concerning (i) significant deficiencies in the
                  design or operation of internal controls which could adversely
                  affect the Company's ability to record, process, summarize and
                  report financial data or (ii) any fraud, whether or not
                  material, that involves management or other employees who have
                  a significant role in the Company's financial reporting,
                  disclosures or internal controls.

V.       COMPLIANCE WITH APPLICABLE LAWS, RULES AND REGULATIONS

                  The Senior Financial Officers should encourage and promote
         compliance by all employees of the Company, its subsidiaries and
         affiliated entities with the laws, rules and regulations applicable to
         their business and operations, including the retention and disposal of
         business documents and records.

VI.      REPORTING CODE VIOLATIONS

                  Senior Financial Officers should report to the Company's chief
         executive officer and to the Audit Committee (and any other appropriate
         committee thereof) of the Board any known or suspected violation of
         this Code by any Senior Financial Officer.

                                        2
<PAGE>

VII.     CONSEQUENCES FOR NON-ADHERENCE TO CODE PROVISIONS

                  Each Senior Financial Officer shall be personally responsible
         and accountable for his or her adherence to the provisions of this Code
         in all material respects. The Company, at the direction of the Board
         (or the Audit Committee or other appropriate committee thereof), may
         impose such sanctions, including dismissal for cause, for a Senior
         Financial Officer's violation of this Code as the Board (or the Audit
         Committee or other appropriate committee thereof) shall determine,
         under the circumstances, to be in the best interests of the Company and
         its stockholders.

VIII.    WAIVER AND AMENDMENT OF THE CODE

                  Any waiver of this Code may be made only by the Board (or the
         Audit Committee or other appropriate committee thereof) and must be
         reported and disclosed as required by and in accordance with applicable
         laws, rules and regulations.

                  This Code may be amended from time to time by the Board or an
         appropriate committee thereof and any amendment must be reported and
         disclosed as required by and in accordance with applicable laws, rules
         and regulations.

                                        3