DEVELOPMENTAL CORE ABSRACT HIV has the highest prevalence in the US among marginalized populations, including African-American and Latinx communities as well as sexual and gender diverse individuals. Therefore, ending the US epidemic will require innovative research to inform services that can reach the most marginalized populations. One way to achieve this is to ensure that individuals from groups underrepresented in science enter the pipeline for career development. Methodologically strong investigators from diverse communities are necessary to expand research and community networks and implement innovative and effective interventions to address co-morbid mental health problems and HIV. In addition, they must possess cultural fluency and an intimate understanding of what makes programs sustainable locally. In an innovative response to these needs, the University of Washington (UW) Developmental AIDS Research Center (D-ARC) Developmental Core team aims to 1) Attract, engage, and support a diverse set of early stage investigators (ESI) in mental health and HIV research and 2) Enhance the mentoring skills of mental health and HIV researchers to promote a nurturing environment for ESI. Culturally informed mentorship is essential to increasing the quantity and diversity of investigators for the HIV behavioral research workforce. Thus, we will use an established Mentoring the Mentors (MtM) curriculum for ongoing cohorts of US and sub-Saharan African mentors. The Core will leverage existing strengths and institutional support at UW, including from the UW/Fred Hutch CFAR (which has generously provided four 2-year New Investigator Awards for mental health and HIV, to supplement the Core’s ten 2-year Synergistic Pilot ARC [SPARC] awards and eight Travel Awards). The Core will connect ESI with mentors from an extensive network of UW investigators with relevant methodological and implementation science expertise and strengthen access to NIH-funded centers (e.g., ALACRITY), NIAID-funded clinical trial networks (e.g., HPTN, HVTN, IMPAACT, MTN), and the NIMH-funded U19 Scale-Up Hub Networks. Finally, the Core will leverage UW graduate school offerings, e-learning methods courses, and global trainings in state-of-the-art implementation science. Overall, the Core will add value by synergizing local expertise in mental health and HIV to develop a diverse group of independent scholars and supportive mentors, each capable of conducting the rigorous, innovative science needed to end the HIV epidemic.