Background: Despite the popularity of epidural bupivacaine-morphine infusions for postoperative pain management, the optimum concentrations and dosages of bupivacaine have not been determined. At present, due to the disadvantages conferred by intense motor block and the increased risk of toxicity, many trials focus on reducing bupivacaine concentration and thus the evaluation of concentrations less than 0.1% may be warranted. Methods: Forty patients having epiduro-general anesthesia for hysterectomy were randomly assigned to one of two study groups. As a mean of postoperative pain control, all received 2 mg of epidural morphine bolusly 1 hr before the end of surgery and continuous epidural infusion was started using a two-day Infusor containing 4 mg of morphine in 100 ml of 0.125% bupivacaine (Group 0.125B, n=20) or 100 ml of 0.0625% bupivacaine (Group 0.0625B, n=20). Study endpoints included visual analog scales (VAS) for pain during rest and movement, sensory change and motor blockade. They were assessed at 2, 4, 8, 16, 24, 32, 40 and 48 hrs postoperatively. Results: For VAS during rest, no significance could be found between two groups over the course of study. But for VAS during movement, the 0.125B group showed more satisfactory results especially during early postoperative periods. For the incidence of complications, the 0.125B group revealed greater frequency of sensory change (25.0%) and motor blockade (10.0%) compared with the 0.0625B group. Conclusion: This study suggests that 0.0625% bupivacaine with morphine via epidural route was sufficient for pain control during rest but it was not satisfactory during movement especially in early postoperative periods. We also recommend that careful attention to motor blockade should be paid when using 0.125% bupivacaine.