MRI and ¹H-MRS show a diffuse abnormality in the brain parenchyma of patients with chronic hepatic failure. These findings support the recently-suggested hypothesis that hepatic encephalopathy is the clinical manifestation of astrocyte swelling produced by hyperammoniemia. Although signal abnormalities within the brain indicating edema have not been described on conventional MRI studies, we have found asymptomatic symmetrical high signal intensity in the hemispheric corticospinal tract on T2WI in the majority of cirrhotic patients. The reversibility of T2 signal abnormalities after normalization of liver function and their time-course correlation with ¹H-MRS and MTR changes support the hypothesis of astrocytic swelling as their origin. Preliminary studies that used DW MRI have shown a reversible and widespread restricted diffusion in the brain white matter that further supports astrocytic swelling as the cause of increased in brain water content. MR may prove useful for studying the effects of therapeutic measures aimed at decreasing brain edema in hepatic encephalopathy.