Project Summary/Abstract In response to CDC’s RFA-CE-22-004 (Research Objective 1, Funding Option B), we propose to conduct a nationally representative 3-wave longitudinal survey of 2,750 youth and young adults ages 10-34 to identify risk and protective factors associated with indirect (witnessing) and direct (gun carrying, perpetration, and victimization) firearm violence in the US. The nationally representative sample will be recruited through NORC’s AmeriSpeak Panel®. This study, guided by the Socio-Ecological Framework and a life course perspective, will provide critical data to better identify youth and young adults at risk for firearm violence, including past and concurrent factors from individual, family, peer, school/work, and community contexts that may amplify risk and lead to different types of firearm violence. We will investigate how factors from these domains function in three developmental periods (10-17, 18-24, 25-34 years of age). Specific aims of the project are to: (SA1) provide population-based estimates of direct (perpetration, gun carrying and victimization) and indirect (witnessing) firearm violence; (SA2) identify the individual, relational (peer, family, romantic partner), school/workplace, and community-level risk and protective factors associated with indirect and direct firearm violence; and (SA3) understand the factors under which youth and young adults have the opportunity and engage in bystander behavior to help prevent firearm violence. Using a nationally representative longitudinal design rarely used in this field, this study will address gaps in the research by comparing how risk factors vary across youth and young adult developmental periods, examining detailed measures of modifiable protective factors, comparing how different forms of firearm violence co-relate, and examining “bystander behavior” in reducing firearm violence. Descriptive and bivariate analyses will be conducted for each specific aim to identify overall prevalence rates of firearm exposure and disparities in exposure by subgroup, and more advanced modeling techniques such as latent class analysis and structural equation modelling will be used to examine the relationship between risk/protective factors and outcomes of interest. Our interdisciplinary team from NORC at the University of Chicago (lead) and the University of New Hampshire specializes in violence prevention research, and has expertise in data linkages, longitudinal analyses, and multi-level modeling. Population-based studies, like the one proposed here, are critical for informing the development of primary and secondary prevention and intervention efforts that are applicable to a broad spectrum of youth and young adults as well as those who represent high risk for firearm violence exposure.