BACKGROUND: Buprenorphine is more potent and has less side effects than morphine. Therefore it can be used instead of morphine in cancer or postoperative pain contol. The aim of this study was to find an effective low dose of buprenorphine in epidural administration for pain control after obstetric-gynecologic surgery. METHODS: Epidural catheters were placed at L2-3 or L3-4 epidural space in all groups. Sixty nine patients were randomized to three epidural infusion group M, B1 and B2. Each group was 23. Group M: 3 mg morphine with 0.5% bupivacaine 10 ml as bolus, morphine 7 mg in 0.125% bupivacaine 100 ml in infusor; group B1: 0.068 mg buprenorphine with 0.5% bupivacaine 10 ml as bolus, buprenorphine 0.17 mg in 0.125% bupivacaine 100 ml in infusor; group B2: 0.11 mg buprenorphine with 0.5% bupivacaine 10ml as bolus, buprenorphine 0.24 mg in 0.125% bupivacaine 100 ml in infusor. Pain score, side effects and frequency of adjuvant analgesics were recorded at postoperative 1, 2, 6, 12, 24 and 48 hours. RESULTS: There was statistically significant difference of pain score at postoperative 1, 2 and 12 hrs in group B1 (p<0.05). Frequency of adjuvant analgesic was significantly increased in group B1. But there was no significant difference between group M and B2 in pain score. CONCLUSIONS: Our results suggest that buprenorphine 0.11 mg as bolus and 0.24 mg for 2 days are the optimal dose in continuous epidural administration for postoperative pain contol.