Acute gastroenteritis is a common disease especially in children. With bronchiolitis and influenza, she participated widely in weight of winter epidemics that causes problems every year our health care system, particularly in the pediatric emergency and inpatient since they are the second leading cause of hospitalization in children. The main symptoms of viral acute gastroenteritis are diarrhea and vomiting which exposes children to the risk of sometimes severe dehydration, the most common cause of hospitalization. There is no specific treatment for these infections. At most, there is a vaccine against severe rotavirus diarrhea (Rotarix ® and RotaTeq ®), but does not yet official recommendations to use in France. The treatment of acute gastroenteritis virus is symptomatic and is generally based on the use of oral rehydration solutions (ORS) whose administration is limited by the frequent presence of vomiting. Until now, no treatment has demonstrated its effectiveness on vomiting due to acute gastroenteritis virus in children. Conventional anti-emetics, widely prescribed, are ineffective in practice, very few studies in this indication and encumbered side effects. Several drugs have long been used in children to fight against severe vomiting associated with the administration of anti-cancer chemotherapy, such as granisetron (Kytril ®) and ondansetron (Zofren ®). The mechanism of action of these molecules is well known. They act both on the enteric nervous system by blocking serotonin receptors. Several placebo-controlled trials suggest that ondansetron is effective in reducing the number of vomiting in children emergency consultant for acute gastroenteritis. However, the method used in these tests and the number of children enrolled has not yet demonstrated the efficacy of ondansetron on the number of admissions, the number of emergency and return the cost / benefit ratio of this treatment. In addition, several studies reported the occurrence of watery stools more frequently in children treated with the placebo group.