Postoperative nausea and vomiting (PONV) after laparoscopic surgery is a common complication. In this prospective, randomized, double-blind, controlled study, we evaluated the efficacy of intravenous droperidol and dexamethasone compared with a saline solution for antiemetic prophylaxis. Methods : Ninety patients, ASA I-II requiring general anesthesia for diagnostic laparoscopy were randomly assigned into three groups (30 each). After induction and intubation, the patients received deoperidol (0.02 mg/kg), dexamethasone (0.2 mg/kg) or saline solution, then were maintained under anesthesia using the balanced technique. Results : The incidence of early PONV in the droperidol and dexamethasone groups was less than that of in the saline group (P<0.05) whereas the incidence in the dexamethasone group was less that that of in the dexamethasone group was less than that of in the deoperidol group (P <0.05). However, the incidence of late PONV in the dexamethasone group was not significantly different from the deoperidol of saline groups (P=0.44). The overall indidence of PONV in the dexamethasone group was less than that of in the droperidol and saline groups (16.7 vs. 30 and 57.7 percents, respectively) but the incidence of severe PONV (N/V score grade 3) in the droperidol group was less than the dexamethasone and saline groups (0 vs. 3 and 3 percents, respectively). There was difference in the sedation score between droperidol and dexamethasone group at 30 min (P=0.01). Three percents of patients in the dexamethasone group received rescue antiemetics vs 6 percents in both the droperidol and saline groups. Conclusion : Dexamethasone is more effective in prophylaxis of early and late PONV than droperidol but do not reduce the severity of PONV.