BACKGROUND: Ondansetron, a 5-HT3 (hydroxytryptamine receptor 3) receptor antagonist, is effective for prevention and treatment of postoperative nausea and vomiting. This study is to evaluate the intraoperative and postoperative efficacy of prophylactic ondansetron and droperidol in preventing nausea and vomiting in cesarean section patients under epidural anesthesia. METHODS: Sixty ASA physical status I-II parturients undergoing elective cesarean section under epidural anesthesia were allocated to 3 groups received intravenous ondansetron 4 mg (Group O), droperidol 1.25 mg (Group D) and normal saline 1 ml (Group N) after delivery of baby. The intra and postoperative incidence and severity of nausea and vomiting were recorded using 4 point scale (0: none, 1 : mild, 2: moderate, 3: severe). RESULTS: There were significantly lower incidence and severity of nausea and vomiting in Group O and Group D than in Group N during intra and postoperative 24 hours (p<0.05). CONCLUSIONS: Prophylactic ondansetron and droperidol had antiemetic effect in cesarean section patients under epidural anesthesia and these effect was observed long after the normal expected duration.