Wernicke's encephalopathy and Korsakoff's psychosis are severe unfavorable forms of alcoholic brain damage with poor prognosis. Thiamine deficiency represents a common cause of both diseases. In many cases, Korsakoff's psychosis develops in the outcome of Wernicke's encephalopathy, which, along with the general etiology, lets talk about a single disease - Wernicke-Korsakoff syndrome, acute (usually reversible) stage of which is Wernicke's encephalopathy and a chronic one (often irreversible) is Korsakoff psychosis. The dramatic paradox of Wernicke's encephalopathy is that in most cases it is difficult to detect, but early diagnosed cases are quite easy to cure. Unrecognized and therefore go untreated Wernicke's encephalopathy is a serious threat to the health and lives of patients, worsens the processes of brain aging and increases the risk of Alzheimer's disease in later life. The basic approach to the treatment of Wernicke-Korsakoff syndrome is long-term parenteral administration of thiamine, often in high doses. As an adjuvant means of therapy memantine is considered.