Exhibit 31.1

RULE 13a-14(a) CERTIFICATION IN ACCORDANCE WITH SECTION 302 OF THESARBANES-OXLEY ACT OF 2002

I, Joel F. Gemunder, President and Chief Executive Officer of Omnicare, Inc. (the Company), certify that:

|1. | I have reviewed this report on Form 10-Q of the Company;                                                                                                                                                                                                                                                                      
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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 Company as of, and for, the periods presented in this report;                                          
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|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)) and
internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the Company and have:
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|   | a)                                                                                                                                                                                                                                                                                                                            
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|   | b)                                                                                                                                                                                                                                                                                                                            
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|   | c)                                                                                                                                                                                                                                                                                                                            
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|   | d)                                                                                                                                                                                                                                                                                                                            
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|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:                                                                                         
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|   | a)                                                                                                                                                                                                                                                                                                                            
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|   | b)                                                                                                                                                                                                                                                                                                                            

Date: May 10, 2007

/s/ Joel F. GemunderJoel F. GemunderPresident and Chief Executive Officer


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