PROJECT ABSTRACT Globally, more than 3.5 million people are infected with hepatitis C virus (HCV). In the United States, due to the opioid epidemic, HCV cases have increased, especially among adults under 30. However, few young people who inject drugs (PWID ≤30 years old) – who are at the center of the HCV epidemic in the US – are benefiting from curative HCV therapy. A potentially promising, yet untapped avenue for increasing HCV treatment among PWID is the leveraging of their injecting partners to successfully navigate the multiple obstacles between diagnosis and treatment. Our team’s extensive research with dyads identified a potential action-point within injecting partnerships that can be harnessed through behavioral intervention. Quantitative findings identified specific injecting related interpersonal factors (i.e., trust, intimacy, cooperation) associated with increased health and safety for injecting partnerships. Followed by qualitative results that in combination with interpersonal factors, partner involvement (i.e., emotional, tangible, affectionate, and positive social support) enhances a partnership’s ability to coordinate behavior (dyadic capacity). Interpersonal factors with partner involvement was found to overcome barriers to HCV treatment. Building on our extensive foundation of dyadic research and dyadic behavior change theories, we developed the Partner Navigation Intervention a two-session injecting partnership intervention to enhance dyadic capacity for HCV treatment initiation for young adult PWID. The proposed study is a randomized controlled study (RCT) to assess the efficacy and mechanism of action of the first behavioral intervention to increase HCV treatment initiation among young adult PWID. In partnership with our community-based HCV testing organizations (CBOs), we will randomize young adult PWID with recently diagnosed HCV infection (250 partnerships, n=500) and their primary injecting partner to intervention or standard of care. Scalability was core to the design of the two-session intervention. Session 1 expands on standard-of-care HCV infection diagnosis counseling with counselor-led discussion with the HCV positive PWID to identify situational and personal barriers to HCV treatment and identify an injecting partner to aid in their HCV treatment navigation. Session 2 is a dyad session with both the young adult PWID and their injecting partner. A counselor facilitated discussion will develop strategies to respond to the identified HCV treatment initiation barriers and partnerships practice strategies and concretize a plan involving both partners for addressing barriers, including a timeline and potential alternative strategies in treatment navigation. During both sessions the counselor records key information discussed onto a paper handout (Partner Navigation Map) serving as the intervention tool. A community advisory board young adult PWID will guide implementation and dissemination. The proposed study will impr...