Tropisetron (Navoban, Sandoz Pharma Ltd., Basel, Switzerland), a selective antagonist of the serotonin receptor (5-HT3) dosed once-daily at 0.2 mg/kg (with a maximum of 5 mg daily), was evaluated in the prevention of chemotherapy-induced nausea and vomiting in 131 children with a median age of 5 years (age 10 weeks to 21 years). Acute lymphocytic leukemia was the most common malignancy (49%). Most children (82%) had received cytotoxic chemotherapy before enrollment. Patients received tropisetron during one or more courses of chemotherapy (455 courses in total). Tropisetron was administered slowly intravenously as a single dose before the start of chemotherapy on day 1 and intravenously or by mouth the subsequent days as a single daily dose (median treatment duration: 5 days). Response to tropisetron per 24 hour period on the first 5 days of each chemotherapy course was graded as complete (absence of both nausea and vomiting), partial (one to four vomits and/or less than 5 hours of nausea), or failure. Overall complete response on day 1 was observed in 305 out of 455 chemotherapy courses (67%). The patients receiving intravenous chemotherapy (N = 92) had a 70% complete response rate and a 26% partial response rate on day 1, both for course 1 and course 2. The percentage of complete responders increased the subsequent days of the course. Emesis after day 1 was observed primarily during courses with the most emetogenic chemotherapy. No side-effects of tropisetron other than a single case of diarrhoea were documented in this study.