The chemical properties, animal and human pharmacology, analgesic efficacy, relative potency, administration, and adverse effects of nalbuphine, a recently marketed, parenteral, strong analgesic with narcotic antagonist properties, are reviewed. Acute, subacute, and chronic toxicity studies in animals revealed no unusual adverse effects. The abuse potential of nalbuphine in man is probably similar to pentazocine. Respiratory depression produced by usual therapeutic doses of nalbuphine is equivalent to that of morphine; at higher than usual doses, nalbuphine produces less respiratory depression. Nalbuphine has few effects on cardiovascular hemodynamics in patients without cardiac disease or with stable ischemic disease. In patients with acute myocardial infarction, nalbuphine has an advantage over morphine, pentazocine, and butorphanol of not producing hypotension. Nalbuphine is as effective and has the same potency as morphine as an analgesic, with about the same onset, peak, and duration of action. Sedation is the most common adverse effect and occurs about as often as with other strong analgesics. Nausea and vomiting occur less often. In contrast to pentazocine, the frequency of psychotomimetic reactions apparently is very low. On the basis of presently available evidence, nalbuphine appears to have fewer disadvantages than any other parenteral strong analgesic.