Performance measurement is the process involving regular data collection and analysis to determine efficacy of programs and services. Whereas businesses have long measured performance success through profits, public agencies are focused on outcome-based performance given that they provide public services. In the United States, federal interest in performance measurement began in 1993 when President Clinton signed the Government Performance and Results Act. Emergency Medical Services for Children is a federally funded program with the overarching mission to improve pediatric outcomes in emergency events by reducing childhood death and disability. The program is an example of almost 2 decades of performance measure development and implementation using Donabedian's 1966 three-element quality health care measurement model: structure, process, and outcome measures. Emergency Medical Services for Children performance measures cover 3 core areas of performance: prehospital, hospital, and program sustainability. These measures represent the only national assessment of the prehospital and hospital infrastructure providing emergency care for children in the United States. In this article, we describe the process, implementation strategies, and lessons learned in the development of the performance measures.