We report on two children with acute encephalopathy showing mild clinical manifestations and reversible white matter lesions. In both patients, MRI revealed high intensities on T2-weighted imaging and marked reductions of water diffusion in the white matter of the bilateral centrum semiovale and the corpus callosum. These abnormalities disappeared along with the neurological symptoms within a week in both patients. These children represent a characteristic group of patients among childhood acute encephalopathy.