The Trauma and Injury Severity Scoring (TRISS) system was developed in the 1980s to improve the prediction of patient outcomes following trauma through the use of physiological and anatomical criteria. The TRISS is used for a number of purposes, including quantifying the severity of injury of a patient population, calculating the probability of survival of patients for identification of cases for peer review, and comparing the death or survival rates of different populations/hospitals. Despite the advancements in trauma care, improved statistical techniques, and the identification of numerous limitations of TRISS, it continues to be the most commonly used tool for judging hospital performance and monitoring trauma death rates. This article critically evaluates the development, structure, and practical use of TRISS to determine its value in the current trauma environment. Limitations of TRISS are discussed and suggestions are made for the future development of trauma prediction tools.