BACKGROUND Droperidol and dimenhydrinate are inexpensive antiemetic drugs. Droperidol, especially, has been studied extensively in the past, but there are no studies that used the combination of both drugs for prevention of postoperative nausea and vomiting (PONV). Thus, the aim of this randomised controlled and double-blinded study was to evaluate the antiemetic efficacy and the side effects of such a combination therapy. METHODS 240 inpatients undergoing ENT surgery under general anaesthesia were randomised to receive one of four antiemetic regimes: placebo, dimenhydrinate (1 mg x kg-1), droperidol (15 micrograms x kg-1), or the combination of both drugs (droperidol 15 micrograms x kg-1 + dimenhydrinate 1 mg x kg-1) was administered after induction of anaesthesia and repeated 6 hours after the first administration. For general anaesthesia a standardised technique including benzodiazepine premedication, propofol, desflurane in N2O/O2, vecuronium, and a continuous infusion of remifentanil was used. Postoperative analgesia and antiemetic rescue medication were standardised. Episodes of vomiting, retching, nausea, and the need for additional antiemetics were recorded for 24 hours. The main goal of the study was to increase the number of patients who were completely free from PONV (chi 2-test with Fisher-Yates' correction). Furthermore, the severity of PONV was analysed using a standardised scoring algorithm. RESULTS Data of 227 patients could be analysed. The incidence of patients who suffered from PONV was 41.3% (95%-confidence interval: 29-55%) in the placebo-group. Dimenhydrinate alone reduced PONV to 34.5% (95%-CI: 22-48%). This marginal effect and the effect of droperidol (PONV: 26.4% (95%-CI: 15-40%)) could not be proven statistically, since the power of the study was too small. The combination of both drugs decreased PONV to 19.6% (95%-CI: 10-32%) and also reduced the severity of the symptoms to a clinically acceptable level. CONCLUSIONS Dimenhydrinate failed to reduce the incidence and severity of PONV. The efficiency of droperidol given alone was within the ranges previously known from metaanalytic data. The combination of both drugs showed a moderate synergistic effect.