['To determine if pH measured at the time of hospital admission and corrected for PCO2 was an independent predictor of trauma survival.', 'Phase 1 was a retrospective case-control analysis of 1708 patients, followed by multivariate multiple logistic regression analysis of a subset of 919 patients for whom the Revised Trauma Score (RTS), Injury Severity Score (ISS), and pH were available. Phase 2 was a prospective comparison of a mathematical model of survival derived in phase 1 (pH-TRISS) with the TRISS method in 508 of 1325 subsequently admitted trauma patients.', 'Urban level 1 trauma center.', 'All patients admitted with blunt or penetrating trauma during the study period.', 'Survival vs mortality.', 'In phase 1, factors significantly associated with mortality by t test and chi 2 analysis included the RTS, ISS< Glasgow Coma Scale, corrected pH (CpH), and sum of the head, chest, and abdominal components of the Abbreviated Injury Scale-85 (AIS85) (HCAISS) (for all, P < .0001). The TRISS statistic was also a significant predictor of survival (P < .004). Age, sex, and the extremity and soft tissue components of the AIS85 were not associated with mortality. In a multivariate analysis of the RTS, HCAISS, and CpH, all were significant predictors of mortality. Even when controlling for RTS and HCAISS, CpH remained a significant predictor of mortality (P < .008). In phase 2, when pH-TRISS was tested prospectively against TRISS in a new group of patients, the new statistic appeared to provide a more accurate prediction of survival.'] Is predictive accuracy of the TRISS survival statistic improved by a modification that includes admission pH?