PROJECT SUMMARY/ABSTRACT Background: Black men who have sex with men (MSM) are disproportionately affected by HIV and other socio-structural factors that contribute to inequities along the HIV prevention and care continuum. Evidence suggests that factors such as housing instability, criminal justice involvement, and unemployment may pose significant barriers to engagement in HIV prevention and care for Black MSM. To date however, existing interventions have been ineffective at addressing these barriers for Black MSM. Because such interventions are resource intensive and logistically challenging, particularly for vulnerable communities who are often highly mobile and less likely to engage in research in traditional settings, guidance is needed at the intervention development stage to determine the most impactful and efficient intervention strategies. Agent-based models (ABMs) provide an opportunity to virtually evaluate candidate interventions to facilitate more efficient and timely intervention development. Because they allow for the conduct of counterfactual experiments, ABMs can also facilitate identification of effects that would be difficult to isolate using traditional approaches and provide valuable insights to guide implementation of HIV prevention interventions. Objective: Building on an existing modeling platform, this proposal will utilize multiple existing data sources to characterize relationships among socio-structural stressors, psychosocial mediators, and HIV prevention and care continuum outcomes among Black MSM and combine methods from implementation science and agent-based modeling to understand the potential impact of structural interventions for reducing HIV transmission. Methods: We will utilize local empirical data to create a realistic synthetic population within an existing agent-based model and apply statistical and computational methods to better understand how socio-structural factors impact engagement in HIV prevention and care continuums. We will then conduct a series of experiments to evaluate how socio- structural factors impact the uptake of existing biomedical interventions and compare outcomes under scenarios with different combinations of interventions Significance: A better understanding of where and how to focus intervention efforts offers potential to improve outcomes along the care continuum by addressing socio-structural barriers to HIV prevention and care engagement for Black MSM. Once developed, our approach can be adapted to other geographic areas to reflect prevention priorities for local health departments and can serve as an example application of ABM methods within implementation science to advance HIV prevention science.