Twenty patients with moderate or severe pain of suspected myocardial infarction received nalbuphine 50 mg intravenously as analgesia in 2 divided doses of 30 mg and 20 mg with 10 mg metoclopramide and were observed for 2 hours. Eighteen patients received nalbuphine outside hospital. The median time from onset of pain to treatment was 73 minutes. Within 30 minutes of the drug's administration 90% of all patients reported satisfactory pain relief (grade 0 or 1). For those with definite myocardial infarction 83% reported satisfactory pain relief at 30 minutes. There were no significant adverse cardiorespiratory effects observed or serious side-effects reported. Nalbuphine is effective and safe when used in this higher dose, although no additional analgesic effect was demonstrated when compared with lower established doses used early in acute myocardial infarction.