• To investigate if cerebral ventricular enlargement is associated with chronic schizophrenia, computerized tomography scans from 73 psychiatric patients were compared with 56 asymptomatic volunteers all less than 50 years old. Ventricular size was significantly greater in the subgroup of 58 chronic schizophrenic patients than in the controls. Of the chronic schizophrenic patients, 40% were outside the control range; 53% exceeded 2 SDs of the control mean. Neither duration of illness nor length of hospitalization correlated with ventricular size. The 44 chronic schizophrenic patients who had never been treated with electroshock therapy (EST) had larger ventricles than controls. A group of seven nonchronic schizophrenic patients also had enlarged ventricles; the eight patients who were either schizoaffective or nonschizophrenic did not differ from controls. This study shows that lateral cerebral ventricular enlargement is associated with chronic schizophrenia; it suggests that this is not a result of treatment.