Epilepsy with an onset of initial episode in adult life is not a rare event. It is generaly considered that the onset of seizure after early adulthood may turn out to be an ominous sign and should be investigated thoroughlyly to rule out an organic brain lesion. The present study of 206 patients with epilepsy of late onset (over 20 years of age), who admitted to or were consulted Department of Neurology, Seoul National University Hospital from January 1982 to December 1985, was undertaken to seek treatable causes and re-evaluate the relationship between clinical evaluation, electroencephalography and computerized tomography of the brain. Patients'ages ranged from 20 to 74.132 were men and 74, women (64% and 36%, respectively). Major causes were infectious or inflammatory origin (45.2%) and cerebrovascular disorders (21.8%). Causes remained unknown in 14.2%. Comparison of the CT findings with EEG showed a close relationship between the local EEG slowing and the focal CT abnormality. Therapeutic responses to antiepileptic drugs were not favorable in patients with encephalitis or meningoencephalitis.