In a large double-blind study of antiemetic therapy conducted in Italy, 289 patients underwent 3 consecutive cycles of cisplatin chemotherapy. Antiemetic treatment with ondansetron plus dexamethasone was more efficacious and better tolerated, but also more expensive, than treatment with metoclopramide plus both dexamethasone and diphenhydramine. To evaluate the different costs of the 2 antiemetic regimens, we conducted a retrospective cost-effectiveness analysis from a hospital perspective. Direct costs of antiemetic therapy (acquisition cost of drugs, materials and time spent by nurses to prepare and administer therapies), cleanup after emesis, rescue medication and adverse events were evaluated. Antiemetic drug acquisition costs per patient were 5.23-fold higher for the ondansetron regimen than for the metoclopramide regimen. However, when the costs of materials and nursing time required to prepare and administer the antiemetic regimens were included, this ratio was 3.77. Furthermore, including the cost of emesis, rescue antiemetic treatments and medication used to treat adverse events, hospital costs per patient were 3.21-fold higher with the ondansetron regimen during the first cycle, 3.08-fold higher during second cycle and 2.89-fold higher during third cycle of chemotherapy. Complete protection from vomiting and from both vomiting and nausea with ondansetron occurred, respectively, in 78.7 and 69.1% of patients in the first cycle, 73.8 and 57.3% in the second cycle, and 74.2 and 58.1% in third cycle of chemotherapy. Corresponding figures for the metoclopramide regimen were 59.5 and 50.4%, 53.6 and 37.1%, and 46.8 and 27.3%, respectively. Thus, the cost per successfully treated (completely protected) patient was 2.43- and 2.34-fold higher, respectively, for ondansetron at the first cycle, 2.23- and 1.99-fold higher, respectively, at second cycle, and 1.82- and 1.36-fold higher, respectively, at third cycle. In conclusion, the study demonstrates that, while ondansetron has a greater acquisition cost than metoclopramide, the ondansetron regimen costs per successfully-treated patient substantially decrease when all direct hospital costs are taken into account.