PROJECT SUMMARY/ABSTRACT Young sexual minority men (YSMM) aged 16-29 are at increased risk of acquiring HIV. YSMM who find themselves in the period of adolescence and emerging adulthood face many physical and psychosocial changes, including potential experiences of discrimination and prejudice due to their sexual minority identity (i.e., minority stress). These experiences in turn may increase their susceptibility to engage in negative health behaviors that place them at higher risk of acquiring HIV, such as substance use and condomless anal sex (CAS). Emerging adulthood has also been found to be the period with the highest reported substance use, and sexual minorities engage in more substance use compared to their heterosexual peers. Furthermore, higher levels of substance use have been associated with higher engagement in CAS. However, while minority stress has been used to understand these disparities, this alone does not explain why Black and Latino YSMM experience an even higher risk of acquiring HIV compared to their White peers despite reporting overall less risky health behaviors. A growing body of literature has begun to highlight intersectional stigma–a form of stigma caused by one's interlocking marginalized identities–as a cause for this disparity. Additionally, research on the underlying mechanisms between intersectional stigma and negative health risk behaviors are understudied, but empirical work suggests social anxiety may play a role in this association. Sexual minorities have been found to meet criteria for social anxiety disorder at higher rates than their heterosexual counterparts, and minority stress has been hypothesized to be a driver of this given the hypervigilance and expectations of rejection these experiences instill on sexual minorities. However, both the prevalence and effects of social anxiety on the negative health behaviors that increase risk of acquiring HIV among Black and Latino YSMM are understudied. Therefore, building off minority stress theory and intersectionality framework, the primary goal of this Diversity-F31 study is to examine the association between intersectional stigma, substance use, and CAS among Black and Latino YSMM, and assess for the role of social anxiety symptomology in these associations. The study focuses on two aims: (1) examine if Black and Latino YSMM who experience clinically elevated levels of social anxiety have stronger associations between experiences of intersectional stigma, substance use, and CAS; and (2) examine the mechanistic role of daily socially anxious symptomology at the within-person level in the association between daily experiences of intersectional stigma, substance use, and CAS. The proposed project will be embedded into a larger daily diary study of intersectional stigma among YSMM (R21-MH121311, PI: Rendina). The proposed project will add daily measures of social anxiety. The research and training plans proposed for this project are also designed to foster my de...