The anti-emetic effects of ondansetron and droperidol were evaluated in 134 ASA Grade I and II female patients, scheduled for laparoscopic cholecystectomy and minor gynaecological laparoscopic surgery, who were randomly assigned to receive ondansetron 4 mg or droperidol 75 μg kg−1 intravenously immediately after induction of anaesthesia. The patients were assessed 1, 6, 12 and 24 h after surgery for intensity of nausea and number of vomiting episodes. In the case of the patients undergoing laparoscopy, vomiting episodes occurred in a similar proportion in patients treated with ondansetron or droperidol, with the probability of the Type I error of 0.05 and the Type error II of 0.1. Although there was no difference between the two groups in emetic episodes following all laparoÍscopic procedures and gynaecological laparoscopic surgery, there was a significant difference between these parameters after laparoscopic cholecystectomy. The patients treated with ondansetron experienced a lower intensity of nausea (P=0.04) after laparoscopic cholecystectomy, less frequent severe nausea (P=0.02) and episodes of vomiting (P=0.04) when compared with those in the droperidol group. We conclude, that despite the result the droperidol prophylaxis appears to be an effective alternative to ondansetron in all patients undergoing laparoscopy, the ondansetron prophylaxis is superior to droperidol in patients undergoing laparoscopic cholecystectomy.