This excerpt taken from the CVS 10-K filed Feb 27, 2007.
Fair value of financial instruments ~ As of December 30, 2006, the Companys financial instruments include cash and cash equivalents, accounts receivable, accounts payable and short-term debt. Due to the short-term nature of these instruments, the Companys carrying value approximates fair value. The carrying amount and the estimated fair value of long-term debt was $3.1 billion as of December 30, 2006. The carrying amount and the estimated fair value of long-term debt was $1.9 billion as of December 31, 2005. The fair value of long-term debt was estimated based on rates currently offered to the Company for debt with similar terms and maturities. The Company had outstanding letters of credit, which guaranteed foreign trade purchases, with a fair value of $6.8 million as of December 30, 2006, and $9.5 million as of December 31, 2005. There were no outstanding investments in derivative financial instruments as of December 30, 2006 or December 31, 2005.