Acute disseminated encephalomyelitis (ADEM) follows certain viral infection or vaccinations, which has a close etiological relationship to experimental autoimmune encephalomyelitis (EAE). Immunological examinations have not been sufficiently carried out on human ADEM except postmeasles encephalomyelitis. The most important pathogenic role in ADEM might be changes of immune regulatory mechanisms by virus infection. Therefore, it would be very useful to investigate cytokine, adhesion molecules and receptors on neural cells and endothelial cells in the central nervous system. Recently, the incidence of postvaccinated encephalomyelitis has reduced. Neurologic complications of immunization have been still reported, however, there is no scientific method to prove that the association is causal or coincidental in an individual case.