Nalbuphine is a narcotic antagonist and analgesic. A dose of 8 mg. per 70 Kg. of nalbuphine in man produces subjective effects which resemble those of 10 mg. per 70 Kg. of morphine. Nalbuphine, in doses of 24 and 72 mg. per 70 Kg., produces mild effects which more closely resemble those of nalorphine. Nalbuphine is ¼ as potent as nalorphine in precipitating abstinence in subjects dependent on 60 mg. of morphine per day. Chronic administration of nalbuphine produces physical dependence which resembles that produced by pentazocine, since it has elements of both morphine and nalorphine dependence. It is concluded that nalbuphine has an abuse potential which approximates that of pentazocine, but equianalgesic doses of nalbuphine produce less nalorphine‐like effects than does pentazocine.