With the purpose of investigating the clinicopathological changes and the criterion for differential diagnosis, ten cases of Acute multiple sclerosis (AMS) were analysed. The data suggested that its clinical course was an acute neurologic event characterized by psychic syndrome, paralysis and incontinence of bowel movement and urination. Pathologically, the demyelination lesion consisted of three patterns, i.e.: vascullar or spongy lesions, shadow plaques and liquefaction or necrosis. One of the above forms could exist individually or coexist with the others. The accurate diagnosis was made only after autopsy. Criterion for the differential diagnosis between AMS and ADEM were discussed.