Computer tomography (CT) of the brain was carried out in 49 schizophrenic patients and 38 controls in order to study the organic characteristics of the brain in schizophrenia. Between the schizophrenic and control groups aged 21 to 40 years, there was no marked difference in ventricular size or cortical atrophy. In the groups aged 41 to 60 years, however, enlargement of the ventricular system and cortical atrophy were highly significant in the schizophrenic group. Positive correlation was observed (P less than 0.05) between enlargement of the third ventricle and duration of illness. There was a high frequency of cortical atrophy in the frontal and temporal lobes in the schizophrenic group.