BACKGROUND Severity-of-illness scoring systems have primarily been developed for, and validated in, younger trauma patients. OBJECTIVE We sought to determine the accuracy of the injury severity score (ISS) and the revised trauma score (RTS) in predicting mortality and hospital length of stay (LOS) in trauma patients over the age of 65 treated in our emergency department (ED). METHODS Using the Illinois Trauma Registry, we identified all patients 65 years and older treated in our level I trauma facility from January 2004 to November 2007. The primary outcome was death; the secondary outcome was overall hospital length of stay (LOS). We measured associations between scores and outcomes with binary logistic and linear regression. RESULTS A total of 347 patients, 65 years of age and older were treated in our hospital during the study period. Median age was 76 years (IQR 69-82), with median ISS 13 (IQR 8-17), and median RTS 7.8 (IQR 7.1-7.8). Overall mortality was 24%. A higher value for ISS showed a positive correlation with likelihood of death, which although statistically significant, was numerically small (OR=1.10, 95% CI 1.06 to 1.13, P<0.001). An elevated RTS had an inverse correlation to likelihood of death that was also statistically significant (OR=0.48, 95% CI 0.39 to 0.58, P<0.001). Total hospital LOS increased with increasing ISS, with statistical significance decreasing at the highest levels of ISS, but an increase in RTS not confirming the predicted decrease in total hospital LOS consistently across all ranges of RTS. CONCLUSIONS The ISS and the RTS were better predictors of mortality than hypothesized, but had limited correlation with hospital LOS in elderly trauma patients. Although there may be some utility in these scores when applied to the elderly population, caution is warranted if attempting to predict the prognosis of patients.