The therapeutic value of buprenorphine was investigated in 31 patients suffering from moderate to severe cancer pain by intramuscular administration at the single doses of 0.2 mg and 0.3 mg in comparison with pentazocine 30 mg. Analgesic effect of buprenorphine 0.3 mg was significantly superior to buprenorphine 0.2 mg and pentazocine 30 mg. The duration of analgesia with buprenorphine was 9 hours at 0.2 mg and 11 hours at 0.3 mg, which were markedly longer than pentazocine's 6 hours. Side effects most commonly observed in the three groups were nausea, vertigo, oral dryness, urinary retention, vomiting, sweating, and headache. The frequency of side effects was 54.8% for buprenorphine 0.2 mg, 50.0% for buprenorphine 0.3 mg and 58.3% for pentazocine 30 mg respectively, indicating no significant difference between the three groups. Blood pressure, heart rate and respiratory rate did not change appreciably, thereby suggesting a little effect of buprenorphine on the respiratory and cardiovascular systems. Buprenorphine was found a useful or extremely useful in 58% at 0.2 mg and 87.5% at 0.3 mg. As the result it was concluded that buprenorphine could be valuable as an analgesic for cancer pain.