Wernicke encephalopathy is a disease usually related to chronic alcoholism. The clinical diagnosis is often difficult to establish, and CT is unable to provide specific findings. MR follow-up studies in five patients affected by Wernicke encephalopathy were performed with the aim of establishing the sensitivity of MR in depicting the typical diencephalic/mesencephalic lesions. All subjects had MR imaging in the acute phase of the disease and were reexamined 6-12 months later, at which time they were in good health. Three of them also had CT scanning. On MR, hyperintense areas seen surrounding the third ventricle and aqueduct during the acute phase of the disease had disappeared or diminished on follow-up evaluations. The third ventricle and aqueduct were dilated. We suggest that these findings reflect the natural evolution of Wernicke encephalopathy. The MR findings in Wernicke encephalopathy enable early diagnosis of the disease, which has a positive effect on both treatment and prognosis.