A prospective interview-based survey on the incidence of postoperative nausea and vomiting in 1107 in-patients aged 4-86 years was conducted during a 3-month period. Nausea, emetic episodes and the need for anti-emetic medication were recorded for 24 h postoperatively. In the recovery room, the incidence of nausea and vomiting was 18% and 5%, respectively. Over the whole 24-h period, these figures were 52% and 25%, respectively; severe nausea was experienced by 8%. The highest incidence of emetic sequelae was observed in gynaecological patients; 52% of the 822 patients who received general anaesthesia and 38% of the 285 patients who received regional anaesthesia reported nausea. The most important predictive factors associated with an increased risk for nausea and vomiting were female gender, a previous history of postoperative sickness, a longer duration of surgery, nonsmoking and a history of motion sickness. Based on these five items, a simple score predicting the risk of nausea and vomiting was constructed with a moderately good discriminating power.