BACKGROUND: Local anesthetics combined with an opiate are frequently used as a postoperative epidural PCA regimen. Ropivacaine is known to have a selective blockade of the sensory nerve without motor blockade. This study is designed to show advantages of ropivacaine over bupivacaine. METHODS: Patients undergoing elective abdominal and orthopedic surgeries were randomly selected and divided into two groups, B and R. The patients in group B and R received 0.2% bupivacaine and 0.2% ropivacaine respectively through an epidural catheter using a PCA pump. Both local anesthetic solutions were mixed with 4 microgram/ml of fentanyl. The PCA pumps of both groups were set in the same manner. A basal rate of 2 ml/hr was infused from 1hour after the onset of surgery. This basal rate was continued postoperatively. A bolus dose and lock out time were set at 2 ml and 20 minutes respectively. The Visual analogue pain scale (VAS), demand dose, complication and additional intramuscular analgesic requirements were checked up to 24 hours after surgery in 6-hour interval. RESULTS: The VAS was significantly lower in group R than in group B at 6, 12, 18 and 24 hours after the surgery (P < 0.05). Total additional bolus doses of the PCA pump were not significantly different in either group at 6, 12, 18 and 24 hours after surgery. The patients in group R showed more satisfaction and less additional intramuscular injections. CONCLUSIONS: 0.2% Ropivacaine, mixed with 4microgram/ml of fentanyl, was more effective than bupivacaine, mixed with the same concentration of fentanyl, in controlling postoperative pain using an epidural PCA pump.