**Exhibit31.1**

 

**CERTIFICATION**

 

I, Deborah Dunsire,certify that:

 

1.     I have reviewed this quarterly report on Form 10-Qof Millennium Pharmaceuticals, Inc.;

 

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

 

3.               Based on my knowledge, the financialstatements, and other financial information included in this report, fairlypresent in all material respects the financial condition, results of operationsand cash flows of the registrant as of, and for, the periods presented in thisreport;

 

4.               The registrant’s other certifying officerand I are responsible for establishing and maintaining disclosure controls andprocedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e))and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and15d-15(f)) for the registrant and have:

 

(a)          Designed such disclosure controls and procedures, orcaused such disclosure controls and procedures to be designed under oursupervision, to ensure that material information relating to the registrant, includingits consolidated subsidiaries, is made known to us by others within thoseentities, particularly during the period in which this report is beingprepared;

 

(b)         Designed such internal control overfinancial reporting, or caused such internal control over financial reportingto be designed under our supervision, to provide reasonable assurance regardingthe reliability of financial reporting and the preparation of financialstatements for external purposes in accordance with generally accepted accountingprinciples;

 

(c)          Evaluated the effectiveness of the registrant’sdisclosure controls and procedures and presented in this report our conclusionsabout the effectiveness of the disclosure controls and procedures, as of theend of the period covered by this report based on such evaluation; and

 

(d)         Disclosed in this report any change in the registrant’sinternal control over financial reporting that occurred during the registrant’smost recent fiscal quarter (the registrant’s fourth fiscal quarter in the caseof an annual report) that has materially affected, or is reasonably likely tomaterially affect, the registrant’s internal control over financial reporting;and

 

5.               The registrant’s other certifying officerand I have disclosed, based on our most recent evaluation of internal controlover financial reporting, to the registrant’s auditors and the audit committeeof the registrant’s board of directors (or persons performing the equivalentfunctions):

 

(a)          All significant deficiencies and material weaknessesin the design or operation of internal control over financial reporting whichare 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 involvesmanagement or other employees who have a significant role in the registrant’sinternal control over financial reporting.

 

 
| Date: May 12, 2008 | /s/ DEBORAH DUNSIRE                    |
|-------------------------|----------------------------------------|
|                    | Deborah Dunsire                        |
|                    | President and Chief  Executive Officer |

 

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