Twenty nonseminomatous testicular cancer patients not pretreated with emetogenic chemotherapy were included in a crossover study of antiemetic therapy. Patients were randomly assigned to receive either nabilone (2 X 2 mg/day) or alizapride (3 X 150 mg/day) prior to beginning low-dose cisplatin chemotherapy. Patients on nabilone had significantly fewer episodes of emesis than those on alizapride (medians, 1.1 vs 2.9; p less than 0.01). Nabilone was superior to alizapride in giving complete relief from nausea (medians, 65% vs 30%; p less than 0.01), and was more effective in shortening the duration of nausea (medians, 1.3 h vs 5.1 h; p less than 0.01); however, it caused more adverse effects. It is concluded that nabilone has greater antiemetic activity than alizapride in young patients receiving low-dose cisplatin chemotherapy. Nabilone dosage should be reduced to decrease the incidence and degree of adverse reactions while leaving the definite antiemetic activity unchanged.