In reporting a sporadic case of Marie's ataxia, which, as has been emphasized,1is the same morbid condition described by Dejerine and Thomas as olivopontocerebellar atrophy, I shall endeavor briefly to contrast the histologic changes in this case with those present in its hereditary form and in the sclerosed and the crossed type of cerebellar atrophy. Since Marie's ataxia is rarer than Friedreich's form, it is usually not recognized and is diagnosed instead as some other degenerative disease process—such as multiple sclerosis. A good instance of such an occurrence is presented by the case recorded here. REPORT OF A CASE History. —A man aged 52, white, was admitted to the Research Hospital on July 15, 1935, because of dizziness, tinnitus, unsteadiness of gait and disturbances of speech—of about three years' duration. During that period he had lost about 40 pounds (18.1 Kg.). The disturbances of gait were evidently of