Drug store chain CVS Caremark Corp. said Tuesday that it's buying Longs Drug Stores Corp. in a deal valued at $2.7 billion, excluding the assumption of debt.

The $71.50 per-share cash offer was announced after the end of trading and is a 32 percent premium over Walnut Creek, Calif.-based Longs' closing price of $54.04.

Longs' shares leaped 30 percent, or $16.21, to $70....