In a series of 121 comatose head-injured patients, computerized tomography (CT) scans were obtained at various intervals after onset of coma. The scans were classified without knowledge of previous scans or of the patient's clinical state, and predictions as to outcome at 1 year were made based on clinical features and CT findings. The state of the basal cisterns as seen on CT scans proved to be a very powerful prognosticator. Subsets of features with the greatest prognostic weight were selected systematically for CT features, clinical features, and for a combination of CT and clinical features. With these features, probability statements were made about death or survival at 1 year. The quality of the predictions was established by comparing them with actual outcome. The percentage of accurate predictions was markedly higher with a combination of clinical and CT features than with clinical or CT features alone.