The origins of trauma systems in the United States date to the 1960s when physicians returning from wars abroad realized that lessons learned from managing military casualties could be applied to civilian traumatic injury. Over the next several decades, trauma centers and then trauma systems began to be developed in an attempt to improve prehospital and acute care for these patients. Although studies of trauma system effectiveness are fraught with methodologic difficulties, several types of studies (panel reviews of preventable deaths, registry studies, and population-based studies), suggest that there may be improvements in mortality when trauma systems are established. Further study needs to focus on other outcomes than mortality, such as return to function after rehabilitation. Pediatric trauma systems have by necessity developed within the "adult" systems in place. The history of pediatric system development and studies assessing outcomes are also discussed. Continued system development, assessment, and educational efforts about how childhood injuries are different are essential to combat this leading killer of children.