We are submitting this application in response to RFA CE-20-006, “Research Grants to Prevent Firearm- Related Violence and Injuries,” with specific regard to Objective One, “research to help inform the development of innovative and promising opportunities to enhance safety and prevent firearm-related injuries, deaths, and crime.” We are applying for Funding Option A, “research projects that rely on existing data.” Firearm violence in the United States is a serious public health concern, with 21,789 intentional violence- related firearm deaths in 2017, one third of whom are in the 15-29 year old age range; and the rates are much higher among African American and Hispanic compared to white youth. We collected longitudinal data from two urban samples at high risk for weapons crimes: Flint, MI (5 waves of data collection on a predominantly African American sample of 426 participants from three starting grade cohorts in 2007 of 2nd, 4th, and 9th graders, with the last assessment in 2019 at ages 20, 22, and 27, respectively) and Jersey City, NJ (4 annual waves of data collection on an ethnically diverse sample of 200 participants starting as high school sophomores in 2016-2017). We used similar measures in both studies (e.g., violence/weapon exposure in the neighborhood, family, and media, social cognitions about violence and weapon exposure, violent and weapon- related behavior), and we used a multi-wave, multi-source methodology (e.g., self-, parent-, and teacher- reports; geospatial crime coding of participants' neighborhoods). By calibrating and integrating data across the two studies, we can now use a robust approach to data analysis to address four specific aims: 1) assess developmental patterns of exposure to violent behavior with weapons (in the neighborhood, family, and violent media), of one's own firearms and other weapon use, and of social cognitions about violence, firearms, and weapons use—with nearly every age between 7 and 27 covered in the combined samples, and the relations among these three trajectories; 2) investigate how social cognitions about violence and weapon use mediate the longitudinal relation between exposure to weapon violence and subsequent engagement in weapon violence; 3) examine whether self-reports of neighborhood firearm crime and geospatial calculations of the same differentially or cumulatively predict trajectories of social cognitions about weapon violence, and in turn, actual self-reported use of guns and other weapons; and 4) investigate how personal risk and protective factors (e.g., sex, cognitive achievement, emotional reactivity to violence) and family or extra-familial contextual factors (e.g., parenting, neighborhood qualities) might moderate the relations. By testing key theoretical propositions concerning mediating cognitive and emotional processes, as well as protective factors, our findings can inform the development of multi-layered community interventions to reduce gun violence among urban youth. O...