Computer tomography brain scans were carried out on 40 patients with schizophrenia or schizo-affective disorder of 2-20 years duration. Ventricular-brain ratio (VBR) was significantly greater than that of the control group. In six patients the VBR exceeded the control mean + 2 s.d. Among the 13 whose VBR was more than 1 s.d. above the control mean, none had schizo-affective disorder, all but one had chronic illness, and patients with negative symptoms and those with premorbid schizoid traits were over-represented. VBR was unrelated to medical history, age, duration of illness, or neuroleptic treatment. It was not associated with neurological 'soft' signs or cognitive deficit. Among chronic patients, clinical features showed no association with ventricular size. The findings suggest that large ventricles may be related to a sub-type of chronic schizophrenia rather than to its particular clinical features.