Background and Aims:Elective lower segment cesarean section under spinal anesthesia is frequently associated with shivering. Ondansetron has been shown to be effective for postspinal shivering. In the present study, we compare the efficacy of ondansetron to prevent postspinal shivering in parturients undergoing cesarean delivery under spinal anesthesia.Materials and Methods:A total of eighty full-term parturients scheduled for elective lower segment cesarean section under spinal anesthesia were randomly allocated into two groups. Group O received 8 mg/4 ml ondansetron, and Group S received 4 ml normal saline intravenously immediately before induction of spinal anesthesia. The level of sensory block, core body temperature, shivering score, and presence or absence of nausea and vomiting during the perioperative period, 1st and 5th min neonates Apgar scores were recorded. The data analysis was carried out with Z-test and Chi-square test.Results:Ten percent (4/40) of patients in Group O and 42.5% (17/40) of patients in Group S had Grade III shivering during the perioperative period and that was treated with intravenous injection tramadol (P = 0.001). Two patients (5%) in ondansetron and 19 patients (47.5%) in control group had nausea and vomiting (P < 0.001) and was treated with intravenous 10 mg metoclopramide. 1st and 5th min Apgar scores of neonates were not statistically different in the groups.Conclusions:Ondansetron is an effective way to prevent shivering, nausea and vomiting during lower segment cesarean section under spinal anesthesia with no effect on Apgar score.