The construction of a revised version of the Estimated Survival Probability Index (or ESP index) is described. The original index had been proposed as a tool that would be useful in grading from hospital medical records the severity of injuries sustained by patients hospitalized with trauma conditions. The revised index (RESP) is based on a data set of 61,419 records. Unlike the ESP, the RESP index is based upon parameters that are age specific and specific to decimal ICDA codes. The RESP is validated by correlating RESP scores with observed mortality by using an independent set of multiple-trauma patients. Overall, a strong monotonic relationship between the RESP index and increasing mortality was demonstrated. Also, the RESP index correlated with mortality in selected subsets of multiple trauma patients with extremely severe injuries. Some uses and limitations of this index are discussed.