BACKGROUND: Postoperative nausea and vomiting (PONV) is one of the most common complications following surgery performed under general anesthesia, especially in female patients. A reduction of PONV would improve the overall satisfaction of patients with their hospital experience and the quality of patient care. We have compared the efficacy of ondansetron to droperidol and saline in the prevention of PONV in 90 ASA 1 and 2 patients undergoing breast surgery. METHODS: Patients were randomly divided into four groups to receive pretreatment with a placebo 20 ml, droperidol 1.25 mg and ondansetron 4 mg, or 8 mg. Postoperatively, all episodes of PONV experienced by the patients during the first 24 hours after anesthesia were recorded by study personnel without knowledge of which antiemetics the patients had received. RESULTS: There was no significant difference in the incidence of PONV between the four groups. No major adverse effects were observed in the ondansetron or droperidol groups. CONCLSIONS: The present study demonstrates that droperidol 1.25 mg, ondansetron 4 mg, or 8 mg IV are not superior to a placebo IV in preventing PONV after breast surgery.