Exhibit 12.01


                                  CERTIFICATION



I, Dr. Greg R. Collier, Chief Executive Officer, certify that:

1. I have reviewed this annual report on Form 20-F of ChemGenex Pharmaceuticals
Limited;

2. Based on my knowledge, this report does not contain any untrue statement of a
material fact or omit to state a material fact necessary to make the statements
made, in light of the circumstances under which such statements were made, not
misleading with respect to the period covered by this report;

3. Based on my knowledge, the financial statements, and other financial
information included in this report, fairly present in all material respects the
financial condition, results of operations and cash flows of the company as of,
and for, the periods presented in this report;

4. The company's other certifying officer and I are responsible for establishing
and maintaining disclosure controls and procedures (as defined in Exchange Act
Rules 13a-15(e) and 15d-15(e)) for the company and have:

                  (a) Designed such disclosure controls and procedures, or
                  caused such disclosure controls and procedures to be designed
                  under our supervision, to ensure that material information
                  relating to the company, including its consolidated
                  subsidiaries, is made known to us by others within those
                  entities, particularly during the period in which this report
                  is being prepared;

                  (b) [Paragraph omitted pursuant to SEC Release Nos. 33-8238
                  and 34-47986]

                  (c) Evaluated the effectiveness of the company's disclosure
                  controls and procedures and presented in this report our
                  conclusions about the effectiveness of the disclosure controls
                  and procedures, as of the end of the period covered by this
                  report based on such evaluation; and

                  (d) Disclosed in this report any change in the company's
                  internal control over financial reporting that occurred during
                  the period covered by the annual report that has materially
                  affected, or is reasonably likely to materially affect the
                  company's internal control over financial reporting; and

5. The company's other certifying officer and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
company's auditors and the audit committee of the company's board of directors
(or persons performing the equivalent functions):

                  (a) All significant deficiencies and material weaknesses in
                  the design or operation of internal control over financial
                  reporting which are reasonably likely to adversely affect the
                  company's ability to record, process, summarize and report
                  financial information; and

                  (b) Any fraud, whether or not material, that involves
                  management or other employees who have a significant role in
                  the company's internal control over financial reporting.



                                                     Date: December 16, 2005

                                                     /s/Greg R. Collier
                                                     Dr. Greg R. Collier
                                                     Chief Executive Officer

     A signed original of this written statement required by Section 302 has
   been provided to ChemGenex Pharmaceuticals Limited and will be retained by
             ChemGenex Pharmaceuticals Limited and furnished to the
          Securities and Exchange Commission or its staff upon request.