Buprenorphine was evaluated for its abuse potential and utility in treating narcotic addiction. The drug was morphine-like but was 25 to 50 times more potent than morphine and was longer-acting. Little if any physical dependence of clinical significance was produced by buprenorphine. The effects of morphine to 120-mg doses were blocked by buprenorphine, a blockade that persisted for 29 1/2 hours. In man, buprenorphine has less intrinsic activity than morphine, and as such, as a low abuse potential. Moreover, the drug has potential for treating narcotic addiction since it is acceptable to addicts, is long-acting, produces a low level of physical dependence such that patients may be easily detoxified, is less toxic than drugs used for maintenance therapy, and blocks the effects of narcotics.