- Hypothesis The survival of severe trauma patients is affected by the implementation of a national trauma system, which brought about developments both at the hospital and prehospital levels during the past decade. Design A retrospective cohort study of all severely injured patients (Injury Severity Score >16) recorded in the Israeli National Trauma Registry at all level I trauma centers in Israel from January 1, 1997, to December 31, 2001. Inpatient death rates were examined overall and by subgroups. Setting The National Trauma Registry includes trauma ( International Statistical Classification of Diseases, 9th Revision, Clinical Modification diagnosis codes 800-959) hospitalizations, patients who were transferred to or from other hospitals, and those who died in the emergency department. It excludes patients who were dead on arrival, discharged following treatment in the emergency department, and patients who do not fall into the definition of trauma. Main Outcome Measure Inpatient death. Results Seven thousand four hundred twenty-three severe trauma patients were recorded. Inpatient death rates decreased significantly from 21.6% in 1997 to 14.7% in 2001. The odds ratios of mortality in 1998 through 2001 vs 1997, adjusted for year, age, sex, penetrating injury, and severity of injury (Injury Severity Score >25), were 0.92, 0.89, 0.70, and 0.65, respectively, confirming the downward trend. Conclusions A steady significant reduction in the inpatient death rate of severe trauma patients hospitalized at all level I trauma centers in Israel between 1997 and 2001 was observed. Although a single factor that explains the reduction was not identified, it is evident that the establishment of the trauma system brought about a significant decrease in mortality. We believe that integrated cooperation of various components of the national trauma system in Israel across the years may explain the reduction.