A retrospective study was carried out of 79 patients with subacute or chronic subdural haematomata. Forty-six (58.2%) had mental changes at admission which were categorised using DSM-III criteria. Delirium was the most frequent mental change, followed by dementia and coma. Three cases of organic affective syndrome were found. In those with mental changes, delirium was significant in older patients (P less than .05) and coma in young patients (P less than .001). Dementia was more common in the elderly. These findings confirm the presence of common mental syndromes in patients with subdural and haematomata and substantiate time-honoured clinical stereotypes.