A retrospective clinical study of 22 heavy alcohol drinkers is reported in which postmortem study showed diffuse chromatolysis of neurons identical to that found in neurological pellagra, associated in 13 cases with Marchiafava-Bignami disease and/or Wernicke-Korsakoff disease. The clinical features included confusion and/or clouding of consciousness, marked oppositional hypertonus (‘gegenhalten’) and myoclonus. Because of the frequent coexistence of other alcoholic encephalopathies in the same patient, alcoholic pellagra was often unrecognized. Fifteen patients received thiamine and pyridoxine therapy without niacin. It appeared to aggravate the neurological state or to trigger the development of alcoholic pellagra encephalopathy in 9 cases. The relationship between pellagra occurring during thiamine and pyridoxine therapy and ‘nicotinic acid deficiency’ is discussed. Multiple vitamin therapy should be given in the treatment of undiagnosed encephalopathies in alcoholic patients.