It has long been appreciated that the chronic abuse of alcohol may lead to a deterioration of intellect, personality, and behavior. Some of the ways in which this comes about are reasonably well established. The dementing diseases of Wernicke-Korsakoff syndrome, pellagra, the nonfamilial form of hepatocerebral degeneration, Marchiafava-Bignami disease, and alcoholic dementia and their relationships to chronic alcoholism are discussed in this article.