BACKGROUND Laparoscopic cholecystectomy is associated with a high incidence of postoperative nausea and vomiting. In this study we investigated comparatively the efficacy of combination therapy with ondansetron plus droperidol versus monotherapy with each agent alone in preventing postoperative nausea and vomiting following elective laparoscopic cholecystectomy. METHODS One hundred twenty-seven patients who underwent elective laparoscopic cholecystectomy under general anesthesia were included in the study, and assigned to one of the following three groups according to the antiemetic drug given intravenously at the end of the surgery: droperidol 1.25 mg in group D, ondansetron 4 mg in group O, and a combination of droperidol and ondansetron at the doses mentioned above in group D + O. Incidence of postoperative nausea and vomiting, and doses of given rescue antiemetics were recorded during the first postoperative day. The total drug cost per patient spent for postoperative nausea and vomiting management (including prophylactic antiemetics plus rescue postoperative antiemetics) was calculated. RESULTS Combination therapy significantly reduced postoperative nausea and vomiting at 30 min, 3 h and 6 h after surgery compared with group D (p < 0.01 for all time points) and O (p < 0.01 at 30 min, p < 0.05 at 3 h) and required less rescue antiemetic treatment (p < 0.01). Total antiemetic cost analyses revealed no significant differences among the three groups (p > 0.05). CONCLUSIONS Pretreatment with ondansetron plus droperidol is more effective than monotherapy in preventing postoperative nausea and vomiting following laparoscopic cholecystectomy, without increasing the cost comparatively.