ABSTRACT The goal of this U24 application is to extend our five-year award as Coordinating Center (CC) for the NICHD-sponsored Adolescent Medicine Trials Network for HIV/AIDS Interventions (ATN) for one additional year. The objective of ATN is to increase awareness among at-risk youth of their HIV status and, for those with HIV, achieve linkage, engagement and retention in the care continuum. Many challenges are faced by adolescents during their transition to young adulthood, resulting from developmental changes, peer influences, identity, and self-esteem formation. Risky behaviors among adolescents, which include engaging in unprotected sexual encounters or sharing nonsterile injecting drug paraphernalia, increase their likelihood of acquiring HIV infection. In the 2013 US Youth Risk Behavior Surveillance Survey (YRBSS), 34% of US high school students reported sexual intercourse during the prior 3 months, of which only 59% indicated condom use during last sexual intercourse. The YRBSS also found that only 13% of students had ever been tested for HIV infection. Given the global burden of new HIV infections among young people, greater involvement of adolescents in biomedical and behavioral HIV research is essential. However, significant individual, operational, and community-level barriers have been recognized to engaging adolescents in clinical prevention trials, which include insufficient understanding of research, need for parental consent, lack of access, mistrust and stigma associated with research participation. For the past five years, the ATN has developed and implemented a comprehensive research portfolio to address these issues. As ATN Coordinating Center, we have supported the Network's research by providing scientific leadership and organizational support for ATN research studies and programs. During this extension year, we will continue to emphasize collaboration and provide experienced leadership to complete and close-out research studies across the network and disseminate findings through our various communication channels. Our research operations and administration teams will continue to provide a solid foundation to ATN by facilitating communication, conducting cross-protocol analyses to leverage Network research, supporting submission of study data to DASH, and supporting abstract and publication preparation and submission. This extension year will allow the extraordinary research conducted during this funding cycle of the ATN to be completed and disseminated for maximum impact on the health of adolescents at risk for or living with HIV/AIDS.