Seek, Test, Treat and Retain For Youth and Young Adults Living with or at High Risk for Acquiring HIV (R01) – The purpose of this Funding Opportunity Announcement (FOA) is to examine delivery models of HIV-focused services (testing, linkage, engagement and retention in care) for high risk or already HIV+ infected youth and young adults. Applications should incorporate substance use into study aims and service delivery objectives should address access to substance use prevention, screening, and treatment. Applications examining interventions that focus only on individual-level behavior and outcomes will be considered non-responsive, given the systemic and structural determinants of serostatus screening, treatment retention and viral suppression, which are the most striking areas of deficit among youth in the Seek, Test, Treat, and Retain continuum of care. The developmental, structural, and systemic factors related to serving youth need to be clearly incorporated into study aims, rather than simple incremental refocusing of existing interventions to younger people. Current Closing Date for Applications: April 14, 2015.