Trauma performance improvement takes its roots from the surgical audit, which began in the nineteenth and earlier twentieth century as a system of counting procedures, complications and deaths. This chapter investigates the development of performance improvement from preventable mortality studies. These studies relied on labor intensive reviews of charts by a panel of experts; assessments were based on empiric knowledge and experience. The concept of trauma audit filters to identify specific cases was based on the use of ideal criteria against which actual performance could be measured. The chapter also investigates institutional trauma registries which have been used to provide an ongoing database of all or various subsets of trauma patients. Evidence-based medicine (EBM) provides the scientific basis for guidelines from which institution specific pathways, protocols, or care plans can be developed. This chapter also discusses the need for better system-wide approaches and measures of quality of life outcomes.