Epilepsy can be divided into dividopathic epilepsy and symptomatic epilepsy according to the existence of underlying organic brain disease. it has been said that the incidence of the symptomatic epilepsy caused by underlying orgainic brain disease is higher in late-onset epilepsy after the age of 20 than in childhood-onset epilepsy. CT is very sensitive and non-invasive method for detection of organic brain disease. 168 cases of late-onset epilepsy after the age of 20 were studied by CT in recent 2 years were analyzed. The results were as follows: 1. The 3rd decade was the most frequent age group, and the ratio of male to female was 2.5:1. 2. Structural abnormality on brain CT was demonstrated in 51.8% of the patient. 3. The older the onset of age was, the higher the rate of the abnormal CT finding, except 5th decade which showed less CT abnormality than 4th decade. 4. The most frequent history related to epilepsy was trauma. 63.1% of the patients had no relevant history; and they showed CT findings of brain tumor, atrophy and infarction in decreasing order of frequency. 5. Abnormal CT finding was demonstrated in 49.2% of normal neurologic examination and in 46.4% of normal EEG study. 6. The most frequent lesion of abnormal CT scan in late-onset epilepsy was 30 cases (18.4%) of brain atrophy. the next frequent lesion was 18 cases (10.7%) of brain tumor. Infarction, parasites and calcification were other frequent lesions.