Buprenorphine, a derivative of the morphine alkaloid thebaine, is a strong analgesic with marked narcotic antagonist activity. In studies in relatively small groups of postoperative patients with moderate to severe pain, one or a few doses of buprenorphine parenterally (by intramuscular or slow intravenous injection) or sublingually were at least as effective as standard doses of other strong analgesics such as morphine, pethidine or pentazocine, and buprenorphine was longer acting than these agents. Only a small number of patients with chronic pain have received repeated doses, but in such patients there was no need for increased doses during several weeks to months of treatment. Buprenorphine appears to produce side effects which are similar to those seen with other morphine-like compounds, including respiratory depression. There is apparently no completely reliable specific antagonist for buprenorphine's respiratory depressant effect, since even very high doses of the antagonist drug naloxone may produce only a partial reversal. The respiratory stimulant drug doxapram has overcome respiratory depression in volunteers and in a few patients in a clinical setting, but such studies have not been done in an overdose situation. Animal studies and a direct addiction study in a few volunteers suggest that the dependence liability of buprenorphine may be lower than that of other older morphine-like drugs. However, a slowly emerging abstinence syndrome did occur on withdrawal after very high doses administered for 1 to 2 months. A definitive statement on the drug's dependence liability and abuse potential cannot be made until it has had much wider use for a longer period of time.