Febrile seizures appearing during acute gastroenteritis have been described in japanese populations. These convulsions are not related to clinical signs of dehydration or electrolyte disorder. This entity was called CwG, benign Convulsions with mild Gastroenteritis. We report the case of a 19 month-old japanese boy who presented with a CwG. We described the characteristic clinical features of this entity and we reviewed the cases reported in literature. The evolution of the CwG is always simple without relapse or side effects. Better understanding will help pediatricians make more accurate diagnosis and avoid treatment even though initial signs might be severe.