OBJECTIVE The objective of this study was to evaluate the efficacy and safety of granisetron (5HT3 receptor antagonist) on the incidence of nausea and vomiting in cesarean deliveries under spinal anesthesia. METHODS In the randomized, double-blind study, 80 parturients received granisetron 40 μg/kg or placebo (n = 40 each) intravenously, immediately after clamping of the fetal umbilical cord. Nausea, vomiting, and adverse events were then observed for 24 h after administration of spinal anesthesia. RESULTS A complete response (defined as no postoperative nausea and vomiting) during 0-4 h after administration of spinal anesthesia was achieved in 80 % of patients with granisetron and in 45 % of patients with placebo. The corresponding incidences during (4-24 h) were 82.5 and 55 % (P value <0.05). No difference in adverse events was observed in any of the groups. CONCLUSIONS Prophylactic use of granisetron is effective for preventing emetic episodes during spinal anesthesia for cesarean delivery.