Injury is an important cause of both morbidity and mortality, particularly in the young. Scoring systems have been developed to establish guidelines of transfer and compare patient outcome, but no scoring system as yet has been constructed that focuses upon immune capability of these patients. We report an outcome predictive score (OPS) which appears to distinguish good outcome from sepsis in patients who survive, and between patients with sepsis who survive from patients with sepsis who die. The score is based on (1) Injury severity score (ISS) expressed as percentage of the 50 per cent lethal dose of injury for age (%LD50), (2) Degree of bacterial contamination at initial injury, (3) The patient's monocyte DR antigen expression. Fifty-one severely injured patients were divided into three groups: (1) A group without infection (N = 15), (2) A major sepsis group which survived (N = 24), (3) A group who died (N = 12). There was no difference between the ISS of these groups. The mean OPS of the good outcome group was significantly less than the mean OPS of both the septic (P less than 0.0002) and dead (P less than 0.00001) groups. The mean OPS of the septic group was also significantly less than the mean of the group that died (P less than 0.002). Identification of high risk patients may be important to determine priority of patient care and to institute additional therapeutic measures.