This NOFO invites applications to participate in a research program cooperative agreement to support the Prevention and Treatment through a Comprehensive Care Continuum for HIV-affected Adolescents in Resource Constrained Settings Implementation Science Network (PATC3H-IN). The Network will expand and/or improve successes achieved by PATC3H to new geographic settings with limited implementation science (IS) research capacity and/or risk populations who are poorly represented in international adolescent HIV research (e.g. sexual and gender minorities; commercial sex workers; drug users) and stimulate much needed IS research in a neglected area of public health significance: prevention of new HIV infections among adolescents at risk and the identification of, and linkage and retention to care of and long-term viral suppression among youth living with HIV in low-to-middle income countries (LMICs).