Current trauma assessment scores do not include an assessment of immune competence and have not been designed to predict late death from or risk of infection. We have compared the use of the Outcome Predictive Score (OPS) with other standard scales to predict clinical outcome after trauma. The OPS combines the Injury Severity Score (ISS) corrected for age (% LD50), degree of bacterial contamination, and monocyte HLA-DR antigen expression on hospital admission. The OPS was compared to the ISS,% LD50, Revised Trauma Score (RTS), Combined Trauma Score-ISS (TRISS), and Anatomical Index (AI). Sixty-one seriously ill patients were studied. Patient outcome was defined as uneventful recovery (n= 18), major infection (n= 27), and death (13 of 16 deaths resulted from infection). The assessment scores were compared for their use in prediction of these outcomes, as well as their ability to distinguish patients with good outcome from those patients who developed major infection or died, and to differentiate survival from death. Only the OPS was able to significantly segregate all five outcome groups (p less than 0.05). Although the age-adjusted ISS distinguished between survival and death (p less than 0.05), only OPS consistently distinguished between good outcome and sepsis/death (p less than 0.05), and therefore best identified the patients who developed infection. AI, RTS, and TRISS had little predictive value.