Diarrhea in childhood is very frequent (two episodes/year/children less of 5 years), rarely fatale (mostly mild) and not requiring additional exploration. But it can justify a hospitalization in case of dehydration (delay of care) or risk of dehydration. It is mainly of viral origin (rotavirus +++) and it has for main complication dehydration. Diagnosis and evaluation of the dehydration, in percentage of loss of weight, must be fast and lead (drive) to a premature correction of hypovolumic shock (or to an accurate fluid management). Main treatment is oral rehydration solutions (ORS), which considerably upset the morbi-mortality, associated with a premature refeeding. Breast-feeding must not be interrupted. Symptomatic treatments and especially antibiotics are not recommended. In case of failure of the rehydration by ORS, alternative is nasogastric tube or intraveinous infusion. Prevention includes essentially the respect of hygienic rules and antirotavirus vaccine.nhttp://www.ncbi.nlm.nih.gov/pubmed/23265760