Part II Exhibit 15.1

Letter re: Unaudited Interim Financial Information

May 5, 2011

The Board of Directors and Shareholders:

CVS Caremark Corporation

We are aware of the incorporation by reference in the Registration Statements (Nos. 333-49407, 333-34927, 333-28043, 333-91253, 333-63664, 333-139470 and 333-141481 on Form S-8 and 333-165672 on Form S-3) of CVS Caremark Corporation of our reports dated May 5, 2011, relating to the unaudited condensed consolidated interim financial statements of CVS Caremark Corporation that are included in its Form 10-Q for the quarter ended March 31, 2011.

/s/ Ernst & Young, LLP

Boston, Massachusetts

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