A 6-year old girl developed acquired aphasia with epilepsy and a paroxysmal EEG (Landau-Kleffner syndrome). Isoelectric CSF focusing showed oligoclonal IgG bands. Small lesions were visualized in periventricular left frontal white matter and right parietal lobe centrum semiovale with magnetic resonance imaging (MRI). After a week of ACTH therapy, the EEG paroxysmal activity disappeared; during the next few months, the language disorder improved. Further MRI examination showed a decrease in size and signal of the left frontal lesions, with localized white matter atrophy, dilatation of the subarachnoidal spaces, and disappearance of the right parietal lesion. The clinical and neuroradiologic features and the laboratory data suggest an acute disseminated encephalomyelitis.