The fallowing study was performed in 100 patients undergoing gynecologic lower abdominal surgery. Analgesic efficacy, changes in arterial blood pressure and heart rate, and incidence of side effect were observed after epidural injection of the drugs. The patients were devided into two groups (N=50). Group I was given a bolus dose of 1 mg morphine in 10 ml of 0.25% bupivacaine followed by continuous epidural infusion of morphine 0.05 mg/ml in 0.15% bupivacaine at 2 ml/hr. Group II was given a bolus dose of 100 ug fentanyl in 10 ml of 0.25% bupivacaine followed by continuous epidural infusion of fentanyl 5 ug/ml in 0.15% bupivacaine at 2 ml/hr. The results were as follows. 1) The pain score (visual analogue pain scale) measured at postoperation 1 hr was significantly decreased in Group II (1.51±1.0) compared to group I (2.20±1.1). Percentage of patients needed supplemental analgesics within postoperation 20 min was significantly lower in Group II (4%) than Group I (16%). 2) The cardiovascular changes for 2 hrs after epidutal injection were not occurred significant in both groups. 3) The incidence of nausea or vomiting was significantly lower in Group II (8%) than Group I (28%). Pruritus occurred also significantly less often in Group lI (6%) than group I (30%). Urinary retention and respiratory depression were not observed.