ABSTRACT In Uganda, 1.5 million individuals are living with HIV where there are persistent gaps in the HIV care continuum and prevention efforts. Barriers such as government funding and political and cultural challenges, have impeded HIV prevention and have led to projections of rapid increases in HIV incidence. HIV prevention advocacy efforts in which people living with HIV (PLWH) initiate conversations about HIV and provide HIV prevention information to people in their social networks can be a low-cost approach to addressing the epidemic. The assessment of social networks in the context of HIV research to date has been cross-sectional, yet network relationships and memberships are dynamic in that they change over the life course, potentially impacting HIV behavior over the time. Thus, using data from the parent study, the proposed supplement seeks to further understand how, when, and why social networks change over time and their impact on HIV prevention behavior and outcomes. The specific aims are: 1) To examine cross-sectional associations between HIV-related outcomes on the part of index PLWH participants (ART adherence, condomless sex, viral suppression among index participants) with individual-level factors (socio-demographic characteristics, social roles, internalized HIV stigma), dyadic-level relational factors (trust, frequency of contact, HIV disclosure, and HIV prevention advocacy with alters), social network composition (e.g., proportion of alters who are stigmatizing, proportion of alters who use PrEP, proportion of alters who are tested for HIV) and network structure (e.g., density or connections among alters) among the PLWH index participants; and 2) To explore longitudinally, over 12 months, how changes in HIV-related outcomes, individual-level factors, and dyadic-level factors change in conjunction with changes in social network composition (e.g., reduced proportion of alters who are stigmatizing, increased proportion who use PrEP and are tested) and structure (e.g., increased density) over time among the PLWH index participants. The proposed supplement study will use data from the parent study’s first 100 PLWH participants and their alters (approximately 300) at baseline and 6- and 12- month follow-up. We will examine cross-sectional associations of network structure and composition with individual- and dyadic-level factors using bivariate cross-tabulations, and regressions using a feature detection approach. Latent growth models (LGM), parallel process LGM and auto-logistic actor attribute models will be used to assess how the network system impacts HIV outcomes longitudinally. This study could greatly aid ongoing efforts to reduce HIV incidence by providing a deeper understanding of the effects of social network dynamics on HIV outcomes across time.