We report two female cases of acute disseminated encephalomyelitis with onset of 19 and 15 months, respectively. MRI demonstrated the T2-high lesions in the cerebral and cerebellar white matter, and the basal ganglia in addition to the spinal cord in the latter case. Treatment with high dose of intravenous methylprednisolone was effective to ameliorate the symptoms in both cases, although spasticity persists in the leg of the latter case. We review ten Japanese cases of acute disseminated encephalomyelitis with the onset before the age of 24 months, including our cases and eight reported cases in the literatures. And we found no significant interrelationships between age of onset and clinical features.