Extensive primary degeneration of the corpus callosum has been described in about forty male Italians. Since Marchiafava and Bignami1reported the first three cases on record, in 1903, the condition has usually been called Marchiafava's disease. It is characterized by demylinization of nerve fibers, with relative retention of axis-cylinders; the lesions occur invariably in the corpus callosum, but sometimes in other parts of the brain as well. These lesions are symmetrically located on the two sides of the brain. In cases in which a clinical history has been obtained the symptoms were found to be both psychic and somatic. The patients were usually in or past middle age and frequently had been excessive users of alcohol. In the present report we shall record an additional case. HISTORY In 1903 Marchiafava and Bignami1reported briefly the observations at autopsy in three cases, one of which had first been described