SummaryThe routine air ventriculograms of 66 psychiatric patients, aged from 22 to 73 years, taken during the psychosurgical operation of stereotactic subcaudate tractotomy, were studied. Ventricular size was unrelated to progressive ageing, but a minority of patients over 60 years had abnormally large ventricles, not invariably associated with cognitive impairment on testing. Enlargement was associated with a clinical diagnosis of schizoaffective illness but not with past ECT.