A total of 2605 old long-stay patients, defined as those admitted to hospital before the age of 65 years and in hospital more than six years, were identified in psychiatric hospitals serving 83% of the Scottish population. The bed occupancy was 59 per 100,000 of the general population, with a range among hospitals of 19-123 per 100,000. Of all patients, 64% were schizophrenic and 15% had organic brain disease; most patients were male, single and over 60 years of age; 41% had been in hospital more than 30 years; 61% had either florid psychotic symptoms or symptoms of a deficit state in marked or severe degree, and the rehabilitation potential for 70% was low. An increasing prevalence of deficit symptoms in schizophrenics was associated with increasing length of stay in hospital; the difference was most marked between those admitted before and after 1953.