SummaryIn this double-blind study the clinical efficacy of a single pre-operative intravenous dose of droperidol 1.25 mg (137 patients), granisetron 1 mg (130 patients) and granisetron 1 mg plus dexamethasone 5 mg (130 patients) was investigated for the prevention of postoperative nausea and vomiting after gynaecological surgery, breast surgery, abdominal surgery and ear, nose and throat surgery. The incidence of nausea in the first 24 h postoperatively was 52% in the droperidol group, 48% in the granisetron group and 34% with the combination, respectively. Both granisetron and granisetron/dexamethasone performed better than droperidol in their effects on vomiting or combined nausea and vomiting (incidence in the first 24 h 22%, 18% and 42%, respectively). The number of emetic episodes during the 5-day study period was significantly higher in the droperidol group (198) than in the granisetron (73) Nausea and vomiting are unpleasant consequences of general anaesthesia. The cause of postoperative nausea and vomiting (PONV) is multifactorial. Several patientrelated factors may affect the incidence of PONV, such as age, gender, weight, motion-sickness and the extent of pre-operative anxiety. Anaesthesia-related factors include the experience of the anaesthetist, premedication, anaesthetic agent (propofol), use of opioids and technique of anaesthesia. The highest incidence of PONV is found in abdominal surgery, gynaecological surgery, laparoscopic surgery, ear nose and throat surgery and breast reductions.