This randomized, double-blind, parallel-group, multicenter study compared the antiemetic effectiveness, safety, and tolerability of two different intravenous (i.v.) doses of dolasetron mesylate (0.6 and 1.8 mg/kg) in cancer patients receiving their first course of high-dose cisplatin-containing chemotherapy (> or = 75 mg/m2). Efficacy was assessed by recording the timing, number, and severity of emetic episodes in the 24 h following high-dose cisplatin. Safety was evaluated by monitoring adverse events, vital signs, clinical laboratory parameters, and electrocardiograms. Of the 62 patients enrolled in the study, 29 received 0.6 mg/kg of dolasetron mesylate and 33 received 1.8 mg/kg. Patients who received dolasetron mesylate 1.8 mg/kg consistently experienced a greater degree of antiemetic control than those who received 0.6 mg/kg. Complete responses were achieved by 55% of patients who received 1.8 mg/kg compared with 31% for the 0.6-mg/kg group. The 1.8-mg/kg group achieved a significantly (p = 0.039) higher complete/ major response rate than the 0.6-mg/kg group (77% vs 55%, respectively) and a significantly (p = 0.004) longer time to the first emetic episode (> 24 h vs 13.5 h, respectively). More than 80% of patients were either satisfied or very satisfied with dolasetron treatment. The most common adverse events were mild to moderate in intensity, consistent with other studies, and included headache (24.1% of patients) and diarrhea (4.8%). These results demonstrated that a single 1.8-mg/kg i.v. dose of dolasetron mesylate provided effective antiemetic activity in a majority of patients given high-dose cisplatin for the first time and should be evaluated further in clinical trials.