Emesis and nausea are common adverse effects of chemotherapy. Consequences include dehydration, acute renal failure, esophageal rupture, electrolyte imbalance and undernutrition, among others. First-generation 5-HT3 antagonists significantly reduce these symptoms but are expensive and require administration every 8-12h. Palonosetron, a second generation 5-HT3 antagonist has proven better results in adult populations. Other benefits include a one-dose administration with effect for up to 7 days and a lower treatment cost. No clinical studies have evaluated the safety and efficacy of palonosetron in children. Prior to every course, patients were randomized to receive palonosetron or ondansetron. Patients or guardians recorded the number of emetic events and the intensity of nausea over a 7-day period. They also reported any possible adverse effects. Statistical analysis included chi(2) test, relative risk, and Student's t test. Fifty courses were analyzed for each group. There was a significant reduction in emesis on the first 3 days and in the intensity of nausea in the first four days in the palonosetron group. There was an increased risk of presenting emesis and nausea in the acute phase when treated with ondansetron. No adverse effects were reported. The cost of treatment was also reduced when using palonosetron. Palonosetron is a safe and effective antiemetic treatment in children, as well as being cost effective.