Droperidol and dimenhydrinate are inexpensive anti-emetic drugs. Droperidol, especially, has been studied extensively, but there are no studies on the combination of both drugs for prevention of post-operative nausea and vomiting. One hundred and forty male hospitalized patients undergoing nasal surgery were randomized to receive one of four anti-emetic regimes: placebo, dimenhydrinate (1 mg kg−1), droperidol (15 μg kg−1), or the combination of both drugs (droperidol 15 μg kg−1+dimenhydrinate 1 mg kg−1) administered after induction of anaesthesia. Patients in the dimenhydrinate-group and the combination-group received a second dose of dimenhydrinate 6 h after the first administration to mitigate the short half-life of the drug. For general anaesthesia a standardized technique, including benzodiazepine premedication, propofol, desflurane in N2O/O2, vecuronium, and a continuous infusion of remifentanil, was used. Post-operative analgesia and anti-emetic rescue medication were standardized. Episodes of vomiting, retching, nausea, and the need for additional anti-emetics were recorded for 24 h. The main endpoint of this study was the number of patients who were completely free of post-operative nausea and vomiting (Fisher's Exact Test) Furthermore, the severity of post-operative nausea and vomiting was analysed using a standardized scoring algorithm. The incidence of patients completely free of post-operative nausea and vomiting was 62.9% in the placebo-group, 77.1% in the dimenhydrinate-group (P =0.21), and 82.9% in the droperidol-group (P =0.07). This increased to 94.3% in the combination-group (P =0.0015). In all three treatment groups the severity of post-operative nausea and vomiting was reduced significantly compared with placebo treatment (P =0.0003). The incidence of side effects was similar in the four groups. Dimenhydrinate was ineffective in reducing the incidence of post-operative nausea and vomiting and droperidol only reduced the severity of post-operative nausea and vomiting. However, the combination of both drugs significantly reduces the incidence of post-operative nausea and vomiting when compared with placebo treatment.