The author has reviewed the outcome of 27 patients aged 75 years and over who had an operation for acute traumatic subdural haematoma at Frenchay Hospital, Bristol, over a 10-year period. There were 15 men and 12 women with a mean age of 79.2 years. The outcome at 6 months was determined using the Glasgow Outcome Score. Of the patients, 15 per cent made a good recovery, 15 per cent a poor recovery and 70 per cent died. The influence of age, sex, mechanism of injury, preoperative Glasgow Coma Score (GCS), pupillary reactivity to light, skull and limb fractures, clinical course, CT scan appearance and timing of operation were analysed in relation to the outcome. The results showed that a preoperative GCS of 4 or less and unilateral pupillary dilatation and non-reactivity to light were not compatible with good survival in the very elderly patient with acute subdural haematoma. Under these circumstances, operation is not justified. The prognosis was worse in patients who were unconscious immediately after injury and with a CT scan showing a subdural haematoma and a haemorrhagic contusion which required urgent early intervention. The prognostic indicators present may prove useful in the selection of patients for active surgical intervention.