PROJECT SUMMARY Alcohol is the most commonly used and abused drug among youth in the US; prevalence of alcohol use is disproportionately higher among sexual minority youth (SMY) than among their heterosexual peers, especially among those at the intersections of multiple marginalized identities. Alcohol use and abuse are associated with a multiplicity of short and long-term negative health outcomes, including HIV vulnerabilities, alcohol and other substance use dependence, neurocognitive deficiencies, and psychological distress. Despite the fact that alcohol use and abuse during adolescence has important consequences for downstream health outcomes and adult patterns of substance use, the majority of research among sexual minorities to date has focused on college-aged populations. This gap in research with SMY is critical to rectify, particularly for SMY who experience multiple, intersecting forms of marginalization based on sex, race/ethnicity, and sexual orientation. Building on our team’s prior work in this area, we propose to use pooled data from the Local Youth Risk Behavior Survey (YRBS), a national biennial survey of high school students that assesses sexual identity and behavior, as well as health behaviors including alcohol use, HIV vulnerability, and mental health. Our uniquely large dataset, which currently contains data from 2005 to 2019 (253 jurisdiction-years) and 950,295 high school youth, will expand to include 2021, 2023, and 2025 data, resulting in an estimated 1,668,078 youth. This will allow us to apply an array of complex epidemiologic approaches to assess the impact of alcohol use on the sexual, mental, and physical health of SMY living in the US, and the disparities that exist between multiply marginalized SMY and their peers. This proposal is a natural extension of our prior work (R01 AA024409) that resulted in numerous publications in high-impact peer-reviewed journals (e.g., Pediatrics, American Journal of Public Health) and a diverse array of interdisciplinary collaborations. The current proposal will continue these successes, incorporating an intersectional lens as well as additional advanced methods of inquiry, including use of multilevel modeling to determine jurisdictional and temporal associations with alcohol use and disparities in HIV risk; latent class analysis to describe alcohol use classes and their association with minority status; and the impact of regional, school, and structural level factors that influence alcohol use and its role in increased HIV vulnerability among diverse SMY. These approaches will allow us to continue identifying critical pathways for intervention to ensure equitable health outcomes and minimize the risks associated with alcohol use and abuse among notably vulnerable populations of youth.