BACKGROUND: Epidural morphine has side effects, especially pruritus, nausea, and vomiting. Butorphanol has been added in studies to reduce these side effects in post cesarean patients. The purpose of this study was to evaluate the side effects and analgesic efficacy when a combination of epidural morphine and butorphanol was administered in patients having combined local anesthetic and opioid epidural infusion. METHODS: Sixty patients having epidural anesthesia for cesarean section were randomly divided into two groups. Group M (n=30) received a bolus of 0.25% bupivacaine 4 ml, morphine 2 mg, and saline 0.75 ml, whereas group B (n=30) received a bolus of 0.25% bupivacaine 4 ml, morphine 2 mg, and butorphanol 1.5 mg (0.75 ml). Continuous epidural infusion was done by Two-day Infusor containing either 0.25% bupivacaine 75 ml, morphine 5 mg, and saline 20 ml in group M or 0.25% bupivacaine 75 ml, morphine 5 mg, butorphanol 4 mg (2 ml), and saline 18 ml in group B. We compared the side effect and analgesic effect of group M to those of group B for 2 days. RESULTS: The incidence of pruritus and vomiting were reduced significantly in group B (p<0.05). There were no significant differences between both groups in the incidence of nausea or other side effects as well as no differences in analgesic effect. CONCLUSIONS: We conclude that the addition of butorphanol to morphine in combined local anesthetic and opioid epidural infusion for postoperative analgesia decreases the occurrence of pruritus and vomiting without significant increase of other side effects and adverse effect on analgesia.