and Specific Aims To harness collective momentum to address the adolescent HIV epidemic in Sub-Saharan Africa (SSA) through implementation science (IS), through the Adolescent HIV Prevention and Treatment Implementation Science Alliance (AHISA) Fogarty?s Center for Global Health Studies proposes to further build research capacity in IS; strengthen locally-led investments in IS; and support collaborations within the alliance of NIH-funded researchers and their in-country counterparts working in this areas. The global HIV response is not adequately addressing the crippling burden of HIV in adolescents. While the overall number of HIV-related deaths has dropped by 30% since its peak in 2005, adolescents have seen a rise in HIV mortality, especially in Sub-Saharan Africa (SSA) where AIDS continues to be the leading cause of death for this age group. Of the estimated 1.8M adolescents living with HIV, 86% live in SSA. In these settings, the benefits of proven interventions have not been fully realized because of enduring barriers to uptake, replication, and scale-up of these interventions. These barriers include a complex array of interpersonal, social, structural, and systems-level obstacles that do not account for the developmental stages of and the many needs specific to adolescents. The field of implementation science (IS) is critical to effectively address these challenges. To make substantial progress, however, increased research capacity in IS is urgently needed, as well as enhanced collaboration, communication, and relationship building among researchers, implementers, policymakers, and adolescents themselves. To this end, the Center for Global Health Studies (CGHS) at the Fogarty International Center (in collaboration with NICHD, NIMH, NIAID, and OAR) launched the Adolescent HIV Prevention and Treatment Implementation Science Alliance (AHISA) in 2017 with initial funding from OGAC (and subsequent funding from OAR). AHISA was developed as an innovative platform to enhance communication and catalyze collaboration among NIH IS-funded researchers and users of research evidence. Through AHISA, these stakeholders comprise a network that facilitates a robust exchange ideas, insights, and experiences as the research progresses and the implementation environment evolves. Building on important advances in the field and a growing portfolio of NIH and global investments in adolescent HIV, AHISA brings together a diverse set of experts working on prevention and treatment of HIV among adolescents from both the United States and SSA and currently includes 75 members. Specifically, AHISA is made up of 26 teams of NIH-funded researchers, program implementers and policymakers working in 11 countries in SSA. The research focuses on challenges to implementing proven interventions and spans prevention and treatment of HIV and includes transitions to adult care, predictors to uptake of and adherence to PrEP, and integrating mental health services in clinical care of adolescents with HIV (Appendix A. AHISA Member?s NIH Funding). The Alliance is guided by a steering committee of experts from NIH?s NICHD, NIMH, NIAID, and OAR, OGAC, USAID, CDC, the Elizabeth Glaser Pediatric AIDS Foundation, the World Health Organization, UNICEF, and the Desmond Tutu Foundation.