Posterior reversible encephalopathy has been reported in patients who receive immunosuppressants. Compared with radiologic studies, electroencephalographic (EEG) findings are not well described. We performed EEG serially in three children who suffered from posterior reversible encephalopathy associated with tacrolimus or cyclosporine. EEG showed continuous focal rhythmic activities in the acute period. EEG findings normalized after the clinical manifestations had disappeared. We conclude that EEG is useful for the diagnosis and follow-up of posterior reversible encephalopathy.