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Exhibit 31.1 
 CERTIFICATIONS I, David G. Nance, certify that:  1.
    
    I have reviewed this Amendment No. 2 on Form 10-K/A of Introgen
Therapeutics, Inc.;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 registrant as of, and for, the periods presented in this report;4.
    
    The registrants other certifying officer(s) 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
registrant 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 registrant, 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) Evaluated the effectiveness of the registrant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(c) 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; and5.
    
    The registrants other certifying officer(s) and I have disclosed,
based on our most recent evaluation of internal control over financial
reporting, to the registrants auditors and the audit committee of the
registrant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 registrant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 registrants internal
control over financial reporting. By:
    
    /s/ David G. NanceDavid G. Nance
Chief Executive Officer
 Date: May 14, 2004




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I, James W. Albrecht, Jr., certify that:  1.
    
    I have reviewed this Amendment No. 2 on Form 10-K/A of Introgen
Therapeutics, Inc.;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 registrant as of, and for, the periods presented in this report;4.
    
    The registrants other certifying officer(s) 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
registrant 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 registrant, 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) Evaluated the effectiveness of the registrant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(c) 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; and5.
    
    The registrants other certifying officer(s) and I have disclosed,
based on our most recent evaluation of internal control over financial
reporting, to the registrants auditors and the audit committee of the
registrant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 registrant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 registrants internal
control over financial reporting. By:
    
    /s/ James W. Albrecht, Jr.James W. Albrecht, Jr.
Chief Financial Officer
 Date: May 14, 2004