<PAGE>
                                                                    Exhibit 31.1

                                CERTIFICATION OF
                             CHIEF EXECUTIVE OFFICER


I, Barry R. Edwards, Chief Executive Officer, certify that:

     1.   I have reviewed this quarterly report on Form 10-Q for the three
          months ended March 31, 2004 of Impax Laboratories, Inc.

     2.   Based on my knowledge, this quarterly 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 quarterly report.

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

     4.   The registrant's other certifying officers and I are responsible for
          establishing and maintaining disclosure controls and procedures (as
          defined in Exchange Act Rules 13a-14 and 15d-14) for the registrant,
          and we have:

          a)   designed such disclosure controls and procedures to ensure that
               material information relating to the registrant, including its
               consolidated subsidiaries, is made known to us by others within
               those entities, particularly during the period in which this
               quarterly report is being prepared;

          b)   (intentionally omitted)

          c)   evaluated the effectiveness of the registrant's disclosure
               controls and procedures; and presented in this quarterly report
               our conclusions about the effectiveness of the disclosure
               controls and procedures based on our evaluation;

          d)   disclosed in this report any change in the registrant's internal
               control over financial reporting that occurred during the
               registrant's most recent fiscal quarter (the registrant's fourth
               fiscal quarter in the case of an annual report) that has
               materially affected, or is reasonably likely to materially
               affect, the registrant's internal control over financial
               reporting, and;

     5.   The registrant's other certifying officers and I have disclosed, based
          on our most recent evaluation, to the registrant's auditors and the
          Audit Committee of registrant's Board of Directors (or persons
          performing the equivalent function):

          a)   all significant deficiencies in the design or operation of
               internal controls which could adversely affect the registrant's
               ability to record, process, summarize, and report financial data,
               and have identified for the registrant's auditors any material
               weaknesses in internal controls; and

          b)   any fraud, whether or not material, that involves management or
               other employees who have a significant role in the registrant's
               internal controls.




                                       /s/  Barry R. Edwards
                                       -----------------------
                                            Barry R. Edwards
                                       Chief Executive Officer


                                             May 5, 2004
                                       -----------------------