This paper reviews data from 3 randomised, double-blind, parallel-group studies carried out in patients receiving high-dose cisplatin chemotherapy (50-120 mg/m2). These comparative trials show that a single intravenous dose of ondansetron (8-32 mg) is as effective as the continuous infusion and intermittent dose regimens used in previous clinical trials (8 mg i.v. followed by a 1 mg/h infusion for 24 h and 0.15 mg/kg i.v. x 3). One of the studies, carried out in Europe, demonstrated that a single 8 mg i.v. dose was as effective as 32 mg given either as an 8 mg loading dose followed by an infusion or as a single intravenous dose of 32 mg before chemotherapy. A similar study conducted in the United States showed that a 32 mg i.v. single dose was significantly more effective than both the 8 mg i.v. dose and the intermittent dose schedule. This study used a prospective stratification based on the dose of cisplatin (50-70 mg/m2 and greater than or equal to 100 mg/m2). In both strata the 32 mg dose was superior. These results emphasise the importance of selecting the dose of ondansetron (8-32 mg) based on factors that predispose patients to emesis, e.g., female gender, patients with a history of chemotherapy or motion sickness and the dose of cisplatin. The ondansetron dosing regimen for patients receiving a highly-emetogenic chemotherapy (8-32 mg i.v. followed by 8 mg orally twice daily) is both simple and flexible.