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Exhibit 31.1
 CERTIFICATION OF CHIEF EXECUTIVE OFFICER
PURSUANT TO EXCHANGE ACT RULES 13a-14(a) and 15d-14(a), AS ADOPTED PURSUANT TO SECTION 302 OF
THE SARBANES-OXLEY ACT OF 2002
  1.
    
    I have reviewed this Quarterly Report on Form 10-Q of Medco Health Solutions, 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 periods covered by this quarterly report;3.
    
    Based on my knowledge, the condensed consolidated 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 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-15f) and 15d-15(f)) for the registrant and we 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 quarterly report is being prepared;b)
    
    Designed such internal control over financial reporting, or caused such internal
control over financial reporting to be designed under our supervision, to provide
reasonable assurance regarding the reliability of financial reporting and the
preparation of financial statements for external reporting purposes in accordance with
generally accepted accounting principles;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, as of the end of the period covered by this
quarterly report based on such evaluation; andd)
    
    Disclosed in this quarterly report any change in the registrants internal control
over financial reporting that occurred during the registrants most recent fiscal
quarter 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 officer 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; andb)
    
    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 B. Snow, Jr.Name:
    
    David B. Snow, Jr.Title:
    
    Chairman and Chief Executive Officer
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