BACKGROUND Use of the trauma and injury severity score (TRISS) for quality and outcomes assessment is challenged by the need for laborious collection of demographic and physiological data. We hypothesize that a novel stratification approach based on International Statistical Classification for Diseases, Ninth Revision (ICD-9) data that are readily available for trauma patients provides a more accurate and more easily obtainable alternative to TRISS with the potential for widespread use. METHODS Data from the ACS National Trauma Data Bank were used to train and evaluate a regularized logistic regression model for mortality and linear regression models for hospital length of stay (HLOS) and intensive care unit length of stay (ILOS) using ICD-9 diagnostic and procedural codes. Model training was performed on data from 2008 (n = 124,625) and evaluation on data from 2009 (n = 120,079). The discrimination and calibration of each model based on ICD-9 codes were compared with those of TRISS. RESULTS The mortality model using ICD-9 codes was comparable with that of TRISS in terms of the area under the receiver operating characteristic curve (0.922 versus 0.921, P = not significant.) and achieved better results in terms of both integrated discrimination improvement (0.106, P < 0.001) and Hosmer-Lemeshow chi-squared value (294.15 versus 2043.20). The HLOS and ILOS models using ICD-9 codes also demonstrated improvements in both R(2) (0.64 versus 0.30 for HLOS, 0.68 versus 0.34 for ILOS) and root mean-squared error (7.06 versus 8.62 for HLOS, 4.15 versus 9.54 for ILOS). CONCLUSIONS Use of ICD-9 codes for stratification provides a more accurate and more broadly applicable approach to quality and outcomes assessment in trauma patients than the labor-intensive gold standard of TRISS.