PROJECT SUMMARY The purpose of this Mentored Research Scientist Career Development Award (K01) application is to develop Dr. Haneefa Saleem’s career as an independent scientist with expertise in social network analysis and the development and evaluation of social network interventions to improve health outcomes. PWID have high rates of HIV, particularly in Tanzania where an estimated 35% of PWID are living with HIV. Methadone maintenance treatment (MMT) is recommended as part of a comprehensive package of interventions for the prevention, treatment, and care of HIV infection among PWID. Retention in MMT is associated with improved antiretroviral therapy (ART) adherence and HIV viral suppression. Retention in MMT is critical for linking PWID to ART services, yet MMT retention is a challenge for PWID who routinely leave treatment in the context of escalating levels of drug use. The goal of this research study is to adapt an innovative social network intervention that mobilizes the personal social networks of treatment-seeking PWID to support them to remain in MMT and adhere to ART in Dar es Salaam, Tanzania. The study’s specific aims are to: 1) qualitatively examine how social networks influence MMT retention and ART adherence among PWID through in-depth interviews with 10 current and 10 former MMT patients; 2) examine the relationship between personal network and network-level factors and MMT retention and ART adherence using egocentric and sociometric network data generated from cross-sectional surveys with 150 HIV-positive MMT patients; and 3) adapt and pilot a social network intervention aimed at improving MMT retention and ART adherence with 15 current HIV-positive MMT patients and 15 of their social support persons to assess intervention acceptability and feasibility in the Tanzanian context. Through the proposed research study and a combination of directed readings, coursework, and mentored research opportunities, Dr. Saleem will be able to achieve the following career development goals: 1) gain expertise in the theoretical underpinnings of social networks; 2) develop advanced social network analysis skills; and 3) enhance her implementation science skills to develop and test social network interventions. To support these goals, Dr. Saleem has a mentoring team of leading experts in social network theory and analysis and social network interventions. Dr. Saleem’s career development and research plan will provide skills and preliminary data for her to pursue future funding and to successfully become an independent researcher in substance use and HIV research both globally and domestically.