Fifty-five schizophrenic, 24 manic and 27 control subjects, all males between 20-45 years of age, were examined for structural brain abnormalities with computerized tomography (CT) scans. Both manic and schizophrenic samples had significantly larger ventricles than the control group. Cerebral atrophy was more frequent in schizophrenia, while cerebellar atrophy was more frequent in mania. An association between increased ventricular size and cerebellar atrophy was found in mania but not in schizophrenia. Cerebral atrophy was not associated with ventricular enlargement in either disorder. Implications of these findings are discussed.