Wernicke's encephalopathy and Korsakoff's psychosis represent a continuum of the same pathologic process. The etiology is an absolute deficiency of thiamine rather than a direct toxic effect of alcohol. The triad of Wernicke's encephalopathy--global confusional state, ophthalmoplegia and nystagmus, and ataxia--is occasionally seen in chronic alcoholics and is often attenuated by immediate thiamine treatment. The triad of Korsakoff's psychosis--memory loss, learning deficits and confabulation--may be seen in either the acute or the long-term care setting.