The efficacy for postoperative analgesia and side-effect of combined epidural infusion of bupivacaine and buprenorphine in comparison with each of these drugs alone were evaluated in 150 patients. All patients received initially bupivacaine 8 ml and buprenorphine 0.1 mg. In a random order, epidural infusion of 5 micrograms.ml-1 buprenorphine 1 ml.h-1 (group A; n = 50), 0.25% bupivacaine 1 ml.h-1 (group B; n = 50), or a combination of the two drugs 1 ml.h-1 (group C; n = 50) was continued for 48 h by a portable disposable device. The analgesic efficacy in group C was superior to that in group A or group B. No significant difference in the incidence of side-effect was found among the three groups. We conclude that epidural analgesia with the combination of buprenorphine and bupivacaine is safe, and easy to manage, giving pain relief superior to that provided by each of these drugs alone.