Acute gastroenteritis results from infection of the gastrointestinal tract, most commonly with a virus. It is characterised by rapid onset of diarrhoea with or without vomiting, nausea, fever, and abdominal pain. Diarrhoea is defined as the frequent passage of unformed, liquid stools. Regardless of the cause, the mainstay of management of acute gastroenteritis is provision of adequate fluids to prevent and treat dehydration.We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of interventions to prevent acute gastroenteritis in children? What are the effects of treatments for acute gastroenteritis in children? We searched: Medline, Embase, The Cochrane Library, and other important databases up to March 2010 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).We found 42 systematic reviews, RCTs, or observational studies that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.In this systematic review, we present information relating to the effectiveness and safety of: rotavirus vaccines for the prevention of gastroenteritis; enteral rehydration solutions (oral or gastric), lactose-free feeds, loperamide, probiotics, and zinc for the treatment of gastroenteritis; and ondansetron for the treatment of vomiting.