BACKGROUND: We designed a randomized study to assess the analgesic efficacy, side effects, and satisfaction score among different doses of butorphanol by using intravenous patient controlled analgesia (IVPCA) for pain relief following a cesarean section. METHODS: Sixty women who received a cesarean section were randomly divided into 3 groups. Each group received butorphanol 3 mg (Group 1), 5 mg (Group 2) or 7 mg (Group 3) with ketorolac 150 mg. Butorphanol and ketorolac were administerd by a two day infusor at the rate of 2 ml/hr. Assessments for pain with NRS, and side effects were evaluated in the recovery room, at 3 hr, 6 hr, 12 hr, 24 hr and 48 hr after the operation. A patient satisfaction score was evaluated at 24 hr and 48 hr after the operation. RESULTS: Pain score at 3 hr after the operation was significantly lower ine Group 2 than Group 1 (P<0.05), at 6 hr and 12 hr after the operation was significantly lower in Group 2 and Group 3 than Group 1 (P<0.05). However, there was no significant difference between Group 2 and Group 3. Patient satisfaction score at 24 hr and 48 hr after the operation did not show any significant difference among the three groups. One patient in Group 2 revealed sedation over 3 on a 4-point scale at 3 hr after the operation, but there was no significant difference among the three groups. CONCLUSIONS: The above results suggested that both butorphanol 5 mg and 7 mg with ketorolac 150 mg via IVPCA were an effective dosage for postoperative pain control during two days after a cesarean section without any significant side effects.