OBJECTIVE: To correlate the MRI findings in acute and chronic stage of Wemicke encephalopathy with the well-known clinical and pathologic findings. Background. Wemicke encephalopathy is an acute phase of Wemicke-Korsakoff syndrome. Pathologic findings change between acute and chronic phases. Only a few MRI studies have been done in this disease to date. METHODS: Ten consecutive patients with Wemicke encephalopathy were evaluated with MRI; seven within 24 hours of thiamine treatment, and three between 2 and 4 days. They presented with confusion, ophthalmoplegia and gait ataxia which improved with intravenous thiamine. Korsakoff psychosis became evident on followup. Tl-, proton- and T2-weighted axial images were obtained with additional 5 mmthick Tl-weighted sagittal and coronal images to evaluate the morphology and size of the mammillary body. RESULTS: Increased T2 signal was seen in the periaqueductal area in seven(sometimes involving superior colliculus); medial thalamus in five; and splenium of the corpus callosum in two. Among the seven patients with T2 signal abnormalities, five had follow-up MRI in 2 to 70 days, which showed complete resolution of the abnormalities. Seven patients showed atrophy of mammillary body on the initial MRI. In the three patients who had normal mammillary body in size on initial scan, follow up MRI revealed atrophic change of mammillary body. Tlweighted sagittal image showed superior cerebellar vermis atrophy in seven. Four patients revealed dilatation of the third ventricle. CONCLUSION: MRI findings of Wernicke encephalopathy appear diagnostic in acute stage and may reflect the pathological evolution in acute and chronic phases of Wernicke-Korsakoff syndrome.