Opioids produce strong analgesic effect result with some side effects such as nausea, vomiting, urinary retention, somnolence, and respiratory depression. Nalbuphine, an agonist-antagonist has, at low doses, an analgesic potency comparable to morphine with little side effects. Analgesic effect after continuous infusion of fentanyl-ketorolac-droperidol, or $Nubain^{(R)}$-ketorolac-dropertiodl combination in Cesarean section patients were assessed by numerical rating scale (NRS) and Prince Hednry scale (PHS). The patients were divided into two groups. Each group consists of 30 patients. Group 1 received 20 ${mu}g$ of fentanyl the end of surgery. And then continuously infused with additional 380${mu}g$ of fentanyl plus 120 mg of ketorolac and 2.5 mg of droperidol. Group 2 initially received 2 mg of $Nubain^{(R)}$ at the end of surgery and the remaining dose of $Nubain^{(R)}$ 38 mg plus ketorolac 120 mg and droperidol 2.5 mg was continuously infused. With all patients, initial dose of drug was administered by bolus of i.v. injection and the remaining dose was administered via i.v. using a Baxter Two $Infusor^{(R)}$. Pain scores and side effects were recorded at the time of recovery room arrival, and at interval of 30 min, 1 hr, 6 hr, 14 hr, 24 hr, 48 hr after start of continuous infusion. No significant difference was found between the pain scores and side effects of both groups although pain control effect was excellent in both groups. We concluded that $Nubain^{(R)}$ could be an alternative to fentanyl for postoperative pain control.