Background: Buprenorphine, a new synthetic thebaine derivative, is a partial agonist of the opioid $mu$-receptor with high receptor affinity, great lipid solubility, and slow rate of opiate receptor association and dissociation. Continuous epidural infusion of opioid can possibly produced undesirable effects, such as respiratory depression, pruritus, etc, in spite of effective postoperative analgesia. Methods: The present study was undertaken to compare the analgesic properties and side effects of continuous epidural infusion of buprenorphine combined with bupivacaine, and morphine combined with bupivacaine in 90 patients following elective gynecologic lower abdominal surgery. At the end of surgery, the initial bolus doses were 3 mg morphine (M group), 0.15 mg buprenorphine (0.15B group), 0.3 mg buprenorphine (0.3B group) combined with 0.25% bupivacaine 10ml, and subsequent continuous infusion doses were 6 mg morphine plus 0.125% bupivacine 100 ml (M group) and 0.6mg buprenorphine plus 0.125% bupivacaine 100 ml (0.15B, 0.3B, group) during 48 hours. The assessment of analgesic efficacy and side effects were made at arrival of recovery room, 1 hr, 4 hr, 8 hr, 24 hr, 36 hr, and 48 hr after the epidural injection. Results: The pain score during 48 hours was significantly higher in the 0.15B group than in the M group and 0.3B group (P<0.05), and the number of patients requiring additional analgesics was significantly higher in the 0.15B group than in the M group and 0.3B group (P<0.05). Signs of respiratory depression were not noted, and the incidence of pruritus, nausea, and vomiting was slightly lower in the 0.15B group and 0.3B group than in the M group, and the incidence of sedation and urinary retention was similar in three group. The subjective rating of satisfaction was better in the 0.3B group than in the M group and 0.15B group (P<0.05). Conclusion: The above results suggest that continuous epidural infusion of buprenorphine combined with low-dose bupivacaine is an advisable method of postoperative analgesia.