This study was designed to evaluate the efficiency of the association ondansetron-dexamethasone during successive courses in 22 chemotherapy-naive female patients receiving a chemotherapy regimen including cisplatin at a dose of 100 mg/m2. The antiemetic treatment consisted of dexamethasone 20 mg i.v. and ondansetron 24 mg i.v. the day of chemotherapy, then ondansetron 8 mg per os every 8 hours for 5 days. A complete control of emesis with no or mild nausea was observed in 41% of cases on the first day of the first course, in 9.5% after the 3rd course. No patient experienced a complete response after the sixth. Similar results were obtained when nausea and vomiting were assessed on the worst day of D2 or D3. Our study shows that, as with other antiemetics, ondansetron-dexamethasone efficiency decreases with the number of courses.