The lack of full correlation between the Injury Severity Score and the resource needs of injured patients STUDY OBJECTIVE: To determine whether the Injury Severity Score (ISS) correlates with the resource requirements of severely injured patients by studying the association of the ISS with three major interventions (fluid resuscitation, invasive central nervous system monitoring, and acute operative repair) trauma centers routinely provide severely injured patients. DESIGN: Retrospective clinical review. SETTING: Level I trauma center. TYPE OF PARTICIPANTS: Eight hundred fourteen adult injured patients. MEASUREMENTS AND MAIN RESULTS: When an ISS of more than 9 was used as the definition of major trauma, the ISS undercorrelated 11% of the time with the need for any one procedure. When an ISS of more than 14 was used as the definition, it undercorrelated 20% of the time. CONCLUSION: The ISS may not be completely correlated with the resource requirements of injured patients and should not be used as the sole means by which to define major injury. 