Part II Exhibit 15.1

Letter re: Unaudited Interim Financial Information

July 28, 2008

The Board of Directors and Shareholders:

CVS Caremark Corporation

We are aware of the incorporation by reference in the Registration Statements (333-49407, 33-40251, 333-34927, 333-28043, 33-17181, 2-97913, 2-77397, 2-53766, 333-91253, 333-141481 and 333-63664 on Form S-8, and 333-134174 and 333-143110 on Form S-3) of CVS Caremark Corporation of our report dated April 29, 2008 and July 28, 2008 relating to the unaudited consolidated condensed interim financial statements of CVS Caremark Corporation that are included in its Form 10-Q for the quarters ended March 29, 2008 and June 28, 2008.

Very truly yours,

/s/ Ernst & Young LLP

Boston, Massachusetts