Project Summary/Abstract HIV is over-represented in substance using and criminal legal involved populations. The syndemic risks for incarceration and HIV risk and acquisition are strongly correlated as a result of both structural and individual- level factors. While effective HIV prevention strategies exist, they are rarely adapted or deployed with people in jails, prisons, during re-entry, or on community supervision. And, when they are, equal collaboration with the community to develop and implement intervention strategies is often missing. Improving meaningful representation of individuals with expertise based on lived experience (“context expertise”), can improve the effectiveness, relevance, validity, and acceptability of health research and service delivery systems. The overall goal of the INTERACT (Using DesIgN jusTicE to impRove cArCeral health ouTcomes) Center is to improve representation and engagement of individuals with context expertise in the criminal legal system, HIV and substance use in research to illuminate key barriers to service access and utilization and identify and test potential solutions that are human-centered and scalable. Our team possesses complementary content and context expertise related to the criminal legal system, and is multidisciplinary (i.e., reflecting training in public health, human-centered design, education, nursing, criminology, social work, community psychology, and cultural anthropology) and multi-tiered (i.e., representing multiple academic roles). As such, we are uniquely positioned to successfully execute all components of this resource center. The specific aims for the INTERACT Center are to: 1) Recruit and engage a Community Advisory Board reflecting context expertise in HIV, substance use, and criminal legal involvement/history; 2) Use human-centered design principles to document experiences with HIV and substance use treatment services and identify strategies to optimize care delivery for future testing; 3) Conduct > two pilot studies, each co-led by a Community Advisory Board member, to explore the feasibility and acceptability of strategies to improve HIV and substance use outcomes; 4) Evaluate the efficacy of the INTERACT Center in supporting the meaningful inclusion of context experts in the development and implementation of HIV and substance use-related research. Successful completion of the proposed aims has the potential to increase trust in health science and improve the availability and desirability of HIV and substance use interventions for a multiply marginalized group.