The investigators conducted a prospective, double-blind randomized trial at a pediatric emergency department in 214 dehydrated children, aged 6 months to 10 years with gastroenteritis and mild to moderate dehydration as assessed by a dehydration score. They were randomly assigned to receive treatment with an ondansetron oral disintegrating tablet or placebo. Oral rehydration was administered according to a standard protocol. The primary outcome was the proportion of children who vomited during oral rehydration therapy. The secondary outcomes were the mean number of episodes of vomiting, and the proportion of children treated with intravenous rehydration or hospitalized.