This study will build upon the research team’s existing work with state laws addressing traumatic brain injury (TBI) and sport-related concussions. It will be the first study to evaluate TBI law data using concussion data from a national surveillance system. The project aims to assess the public health impact of youth sports TBI laws on the rates and patterns of both initial and recurrent concussions among US high school athletes, across a period from pre- to post-law enactment, to determine if the degree of state policy innovation impacts the public health impact of the laws, and to determine if the level of school compliance modifies the public health impact of the laws. The project will use an interrupted time-series research design, analysis of states’ youth sports TBI law data and longitudinal concussion data from athletes in 100 nationally representative high schools collected before and after the laws, and telephone interviews of athletic directors in the 100 high schools to assess their school’s compliance with their respective state’s TBI law. The results will provide empirical evidence on the causal link between the enactment and implementation of TBI laws and the epidemiology of initial and recurrent concussions, and providing practical recommendations for policymakers and schools.