Of 1373 patients who, following severe brain injury had been comatose for over 6 hours, 140 (10%) were in a vegetative state one month later. Fifty-nine regained consciousness but none of those aged over 40 became independent during the first year. Of those still in a vegetative state after 3 months, none became independent irrespective of age. Of all patients comatose for over 6 hours after severe brain injury, only 1% was in a vegetative state after one year. Certain scores for features such as age, pupillary reactions, eye-opening and eye movements indicate either a favourable prognosis, a fatal outcome or irreversible coma. It is only in some 10% of all patients in coma or in a vegetative state during the first two weeks after the accident that it is possible to predict with a high degree of probability (p greater than 0.95), an unfavourable outcome (death or irreversible coma) within one year. At no time after the onset of coma is it possible to predict or distinguish, with a fair degree of probability (e.g. p greater than 0.80), those patients who will remain in a vegetative state from those who will die.