Four normal adult volunteers were given intravenous injections of 16, 32 and 48 mg cocaine, procaine, or saline, once daily in a balanced order. An additional dose of procaine, 96 mg, was also given. Heart rate, blood pressure, and responses on the Profile of Mood States (POMS), Addiction Research Center Inventory (ARCI), and a locally developed drug effects rating scale were measured before and periodically after drug or placebo injection. The profile of action of cocaine was significantly different from that produced by both saline and the lower doses of procaine. Although responses on the ARCI and POMS after all doses of procaine were similar to those obtained after placebo, three of the subjects identified 48 and 96 mg procaine as cocaine, and rated these two drugs similarly at the higher procaine doses.