OBJECTIVE Postoperative nausea and vomiting (PONV) are commonly observed undesirable consequences of laparoscopic cholecystectomy. This study was undertaken to compare granisetron, a selective 5-hydroxytryptamine type 3 receptor antagonist, with droperidol for reducing the incidence and severity of PONV after laparoscopic cholecystectomy. METHODS Eighty patients, aged 25-65 yr, scheduled for elective laparoscopic cholecystectomy were enrolled in a randomized, double-blinded investigation and assigned to one of three treatment regimens: placebo (saline), 1.25 mg droperidol (approximately 25 micrograms.kg-1) or 3 mg granisetron (approximately 60 micrograms.kg-1). The study drugs were administered iv immediately before the induction of anaesthesia. A standard general anaesthetic technique was employed throughout. Nausea, vomiting and safety assessments were performed continuously during the first 24 hr after anaesthesia. RESULTS The incidence of PONV was 46% with placebo, 41% with droperidol and 15% with granisetron (P < 0.05; overall chi 2 test). Four patients who had received placebo and two who had received droperidol required another rescue antiemetic, compared with none who had received granisetron (P < 0.05). Adverse events postoperatively were not different among the groups. CONCLUSIONS Granisetron is more effective than droperidol and placebo for reducing the incidence and severity of PONV after laparoscopic cholecystectomy.