Exhibit 31.1



PRINCIPAL EXECUTIVE OFFICER CERTIFICATION



I, Glenn L. Cooper, Chief Executive Officer of Indevus Pharmaceuticals, Inc. certify that:



|1. | I have reviewed this Quarterly Report on Form 10-Q of Indevus Pharmaceuticals, Inc.;
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|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;
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|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 issuer as of, and for, the periods presented in this report;
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|4. | The issuer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)) [text omitted in accordance with SEC transition instructions] for the issuer and have:
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| | (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 issuer, 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;
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| | (b) | [paragraph omitted in accordance with SEC transition instructions in SEC Release No. 33-8238; 34-47986, Section III.E.];
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| | (c) | Evaluated the effectiveness of the issuer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
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| | (d) | Disclosed in this report any change in the issuers internal control over financial reporting that occurred during the issuers most recent fiscal quarter (the
issuers fourth fiscal quarter in the case of an annual report) that has materially affected, or is reasonably likely to materially affect, the issuers internal control over financial reporting; and
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|5. | The issuers other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to the issuers auditors and
the audit committee of the issuers board of directors (or persons performing the equivalent functions):
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| | (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
issuers ability to record, process, summarize and report financial information; and
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| | (b) | Any fraud, whether or not material, that involves management or other employees who have a significant role in the issuers internal control over financial reporting.
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|Date: May 10, 2005 |  | By: |  | /s/    Glenn L. Cooper 
|                   |  |     |  | Chief Executive Officer