Pharmacological properties of buprenorphine were compared with those of morphine and pentazocine. Buprenorphine scarcely showed any effects on spontaneous EEGs and sleep-wakefulness cycles. Buprenorphine tended to depress the recruiting and augmenting responses and the spindle burst, and it also inhibited the hypothalamic arousal response. Buprenorphine had weaker emetic action than morphine and protected against apomorphine-induced emesis in the same manner as morphine. Buprenorphine scarcely affected respirations, blood pressure, heart rate, blood flow, ECG, cardiac contractile force, cornary flow, and intracranial pressure. However, morphine and pentazocine caused depressed respiration, decreased blood pressure, increased blood flow and cardiac contractile force, and elevated intracranial pressure. Buprenorphine, morphine, and pentazocine did not affect bile secretion, but produced contraction of the sphincter of Oddi. Buprenorphine had very little effect on renal function, but morphine and pentazocine reduced this function to depress urine flow. Buprenorphine and morphine inhibited carrageenin-induced edema. Buprenorphine had no effect on blood histamine level, but morphine increased the concentration of histamine. These results indicate that buprenorphine has little effect on the central nervous system, respiratory and cardiovascular system, and renal function.