1 Human studies at the Addiction Research Center enable narcotic antagonists to be classified into three subgroups: (1) nalorphine-like agents; (2) pure antagonists; and (3) morphine-like agents. 2 Six narcotic antagonists (pentazocine, nalbuphine, cyclazocine, butorphanol, propiram and buprenorphine) developed in recent years seem to have a lesser abuse potential than codeine or propoxyphene. 3 When adjusted for relative availability of the agents, epidemiological data shows that pentazocine is abused less than codeine or propoxyphene in the US. 4 Recent studies with buprenorphine indicate that this agent would find application both as an analgesic of low abuse potential and as a new type of drug for the treatment of addiction.