Acute disseminated encephalomyelitis (ADEM) is an acute inflammatory demyelinating disease of the central nervous system. It is thought to be an autoimmune mediated disorder which occurs usually after viral or bacterial infections, or after immunization. The clinical manifestations reflect sudden onset of the diffuse involvement of the brain, spinal cord and the meninges. We experienced two cases of acute disseminated encephalomyelitis. The diagnoses were made by history, neurologic examination, CSF analysis and brain MRI. The symptoms were improved with steroid treatment. A brief reveiw of literatures also was made.