This randomized double-blind study was undertaken to evaluate the efficacy of ondasetron and dexamathesone in reducing the incidence of postoperative nausea and vomiting after laparoscopic cholecystectomy. The study covered 60 patients (ASA I/II) who had undergone laparoscopic cholecystectomy under general anesthesia. The patients were divided into two groups: 1) 30 patients who received dexamethasone, 4 mg i.v.; and 2) 30 patients who took ondansetron, 4 mg i.v., prior to general anesthesia. Postoperatively, nausea, vomiting, and severe pain (VAS) were observed every 6 hours within the first 24 hours. Postoperative nausea and vomiting occurred in 6 (20) patients in Group I and in 13 (43.33) patients in Group 2 (p < 0.05), while vomiting did only in 5 (16.66%) patients in Group I and 4 (13.33%) in Group 2 (p > 0.05). The least intensity of postoperative pain was observed in Group 1, but the difference between the study groups was insignificant. It is concluded that dexamethasone is more effective in preventing postoperative nausea and vomiting after laparoscopic cholecystectomy than ondansetron. This is mainly determined by a significant reduction in the incidence of postoperative nausea.