We report the electrophysiologic examination of a 55-year-old woman with Werner's syndrome. Needle EMG and peripheral conduction studies were normal. In contrast, EEG was moderately abnormal, the N20 and P25 potentials of SEPs were delayed and enlarged, and the event-related potential, P300, was delayed. These characteristic findings indicated accelerated aging of the brain, as in the other organs, in Werner's syndrome.