How well do regionalized trauma systems work and what affects their performance? This study explored the impact of the structure and organization of regionalized trauma care systems on their effectiveness, measured by patterns of hospital utilization, trauma mortality, financing, and stability. The project surveyed all existing trauma systems in the U.S. to identify key structural features, conduct case studies in areas with trauma systems and areas without such systems to examine the reasons behind the development of particular structures, and conduct descriptive analyses to assess empirically the relationship between structure and performance. The objective of the study was to provide information to state and local policymakers, hospitals, physicians, and other community leaders to help them develop more effective trauma systems, which will be particularly timely in light of legislation passed in 1990 that provided federal funding for regionalized trauma systems.