Abstract Marked disparities by race/ethnicity exist in HIV infection rates and engagement and retention in care among men who have sex with men (MSM) along the HIV care continuum. Compared with White MSM, HIV- infected Black and Hispanic/Latino MSM are less likely to be on antiretroviral therapy (ART), adhere to ART, and achieve viral suppression. Lower rates of care engagement and retention among Black and Latino MSM are influenced by factors beyond the individual. In order to uncover the neighborhood- and network-involved pathways that produce racial/ethnic disparities in HIV care outcomes, yielding an empirical basis for interventions and policies to fill gaps in the care continuum among Black and Latino MSM, systematic, theory- based investigation of the specific and intersecting neighborhood and network characteristics that relate to retention in care, ART adherence, and viral suppression must be engaged. Using socioecological and intersectional conceptual frameworks, several mid-range and micro social and psychological theories, and informed by our NIH/NIMH R56-funded formative research, we propose to identify neighborhood-and network-level characteristics associated with HIV care continuum outcomes (viral suppression, retention in care, and ART adherence) among 550 HIV-infected MSM living in New York City (NYC) via a longitudinal study. We will investigate the influence of neighborhood composition and four neighborhood-level characteristics domains, testing theoretical pathways of influence across the different neighborhoods in which MSM live, socialize, and receive HIV care. The Specific Aims are, among HIV-infected MSM in NYC: Aim 1: To use spatial analysis to characterize clustering and spatial trends in HIV care outcomes. Aim 2: To examine HIV care outcomes by race/ethnicity in relationship to longitudinal changes in: 2a) Exposure to neighborhoods of potential influence (home; social; health facility access); 2b) Neighborhood characteristics conceptual domains (community violence/physical disorder/social disorganization; AOD use factors; social norms; community resources); 2c) Social networks. Aim 3: To use multilevel modeling to assess associations among changes over time in exposure to the neighborhood characteristics and changes in social networks with HIV care outcomes by race/ethnicity, while assessing the potential mediating and moderating effects of individual- and network-level factors. The study will employ an innovative approach combining geospatial mapping of neighborhoods with multilevel modeling, spatial statistics, and an existing, extensive geospatial database. It will have direct implications for the design of multilevel interventions, addressing factors at the neighborhood-, network-, and individual-levels, to improve HIV care outcomes for MSM, particularly for Black and Latino MSM.