OBJECTIVE: Wernicke's encephalopathy (WE) is an acute disorder due to thiamine deficiency, characterized by ophthalmoplegia, ataxia, and mental confusion, similar to that classically observed in alcoholism. Some cases of WE were reported to coincide with other conditions such as hyperemesis gravidarum, bariatric surgery, and total parenteral nutrition. In this study the objective was to retrospectively evaluate the prevalence of WE among intravenously fed patients in our hospital during the previous 2 y. METHODS: Among all cases of WE diagnosed by cranial magnetic resonance scan during a 2-y period in the Azienda Ospedaliera of Padua, we identified patients who exhibited WE during parenteral feeding. Albumin plasma levels, measured at the onset of WE symptoms, were used to estimate nutritional status. RESULTS: We found seven cases of WE that coincided with intravenous feeding. WE occurred, on average, 13 d after the start of glucose infusion. The five subjects with albumin plasma levels lower than 35 g/L at the onset of WE received glucose infusion for fewer days. In six cases the clinical signs disappeared the day after thiamine infusion. In one case mental function did not normalize and the patient developed Korsakoff's syndrome despite prolonged thiamine treatment. CONCLUSION: During a 2-y period we observed a high prevalence of WE in intravenously fed patients due to lack of thiamine supplementation. A prophylactic treatment must be performed in at-risk patients and multivitamin infusion containing thiamine must be administered daily during the course of intravenous feeding.