We evaluated the antiemetic efficacy of tropisetron, a 5-HT3 receptor antagonist, during its use in 15 children with malignant disease who received cisplatin (CDDP) either alone (1/15) or in combination (14/15) with other cytostatic drugs. Tropisetron was given to 15 children (8 boys and 7 girls, ranging from 6 months to 17 years of age) with miscellaneous neoplasms. Generally, tropisetron (5 mg/m2/day, maximum 5 mg/day) was administered intravenously the first day of CDDP-based chemotherapy and orally for 4 subsequent days of chemotherapy. The dose of tropisetron was reduced to 0.2 mg/kg/day in children less than 1 year of age and/or those weighing less than 10 kg. Vomiting and nausea were controlled completely in 8 of 15 (53.3%) children on day 1 with a single intravenous infusion of tropisetron. Partial control was observed in 40% of patients on day 1. Complete control of delayed nausea and vomiting ranged between 40% and 80% in patients over days 2 to 5. The results obtained during administration of tropisetron confirm that it is a valid, safe, and manageable antiemetic for the treatment of malignant disease in pediatric patients.