Computerized axial tomography (CAT) scans were blindly examined, and lateral ventricular-to-brain ratios calculated in 19 schizophrenic and 27 bipolar patients, and in an equal number of individually matched normal controls. Family history, early development, past psychiatric history, and current functioning and symptomatology were analyzed for all patients. Lateral ventricular enlargement on CAT was found in a significant proportion of both patient groups. Patients with such enlargement tended to have greater numbers of negative symptoms and poorer premorbid adjustment, but did not differ regarding family history of psychiatric illness. A subgroup of schizophrenics with presumed early brain damage was identified. This group had more marked ventricular enlargement, a greater number of negative symptoms, and an earlier onset of illness.