PROJECT SUMMARY/ABSTRACT The proposed CFAR/ARC Ending the HIV Epidemic (EHE) supplement will address the “Prevent” Pillar. Social and structural determinants of health are recognized as critical factors in vulnerability to HIV and engagement in HIV prevention and contribute to inequities in HIV experienced by marginalized communities in the U.S. However, HIV services are often siloed from social services, limiting the potential for people with social service needs to also receive HIV prevention services and vice versa, resulting in missed opportunities to improve outcomes along the HIV prevention and care continuum and general well-being of people at risk for HIV. Entre Hermanos, Gay City, and POCAAN are 3 community-based organizations (CBOs) serving diverse populations affected by HIV in King County, WA. They are rooted in HIV prevention and offer HIV/STI testing, PrEP services, and case management and increasingly provide social services, ranging from substance abuse services, immigration legal services, post-incarceration services, to health insurance navigation, with varying levels of service integration. This proposal builds on an existing academic-community partnership and a successful EHE planning project through which we have built consensus around objectives, drivers, and potential approaches for enhancing service integration at each CBO. Here, we propose to evaluate practice facilitation (PF) as an approach to enhance HIV-social service integration and thereby address social determinants of HIV and reduce HIV-related inequities. Practice facilitation is an evidence-based approach for implementing and building capacity for continuous quality improvement (QI) in primary care. Here, it will lead to testing and studying community- driven and -owned practice changes for enhancing service integration, building from ideas generated by CBO staff during the planning project. Our evaluation will be guided by the RE-AIM (Reach, Effectiveness, Adoption, Implementation, Maintenance) framework and supplemented by constructs from Proctor’s Outcome Framework. First, we will analyze programmatic data to evaluate the impact of PF on screening, referrals, and uptake of social services among HIV service clients and for HIV services among social service clients as well as on disparities in these outcomes by key demographics identified by each organization. Second, we will use process data, staff surveys, and focus group discussions with staff to conduct a mixed methods assessment of acceptability, feasibility, appropriateness, adoption implementation, and potential maintenance of PF. Third, we will identify determinants of referral and uptake of social services through focus group discussions with staff. Together, these aims will lead to strengthened, integrated HIV and social service delivery and increased capacity to conduct QI at the three CBOs and identify models for service integration in other settings. Ultimately, the effective integration of social ...