Methods: Two hundred eighty parturients who developed moderate to severe shivering and required treatment after cesarean delivery under spinal anesthesia with bupivacaine and intrathecal morphine 0.2 mg were randomized into 4 groups. Group T, Group N, Group O and Group P were given tramadol 0.5 mg/kg, nalbuphine 0.05 mg/kg, ondansetron 0.1 mg/kg and normal saline 5 mL IV, respectively. The patients were evaluated at 15 minutes after treatment and were observed for a recurrence of PS within 4 hours in a double-blinded fashion. Results: The treatment success rate (no or mild shivering) of PS in groups T, N, O and P were 88, 81, 61 and 36 %, respectively (p<0.001). The treatment success rate of groups T vs P, N vs P, O vs P, T vs O and N vs O were significantly different (p<0.001, 0.001, 0.003, <0.001, and 0.009, respectively). The success rate between groups T vs N was not significantly different (p=0.223). Recurrence rate of PS in groups T, N, O and P were 14 %, 15 %, 11 % and 28 %; p=0.329. Other side effects such as pruritus, nausea/vomiting, and dizziness were few and treatable.