ABSTRACT ?Hierarchical influences on PrEP use, willingness and readiness among male couples? The incidence of HIV continues to increase among men who have sex with men (MSM) continues to increase. Moreover, between one- and two-thirds of MSM in the US acquire HIV from their main partners while in a relationship (i.e., male couples). Although a growing interest in male couples' relationships has emerged in HIV prevention research, few studies have been conducted about their attitudes, support, current use and unsuccessful attempts of obtaining of pre-exposure prophylaxis (PrEP). PrEP ? a daily regimen of ART (i.e., Truvada?) taken by those who are HIV-negative to prevent the acquisition of HIV ? is a promising biomedical approach to preventing new HIV infections among MSM and male couples alike. To date, most research studies have investigated how individual-level factors are associated with MSM's attitudes to use PrEP. Currently, two of CDC's three guidelines for administering PrEP pertain to those who are in a relationship yet very few studies have explored men's perceptions of how casual and main partners affect their PrEP uptake and even fewer studies have collected data from both men of the couple. Beyond the dyadic level of being in a relationship, there is the potential for community and social network factors to shape PrEP attitudes, support, and uptake, but these influences are also largely currently under-explored. To respond to this critical gap in understanding how relational/dyadic, community and social network factors affect PrEP uptake among male couples, we propose to conduct a novel two-year mixed method project to collect in-person, quantitative dyadic data from 100 self-reported HIV-negative and 100 self-reported HIV-discordant male couples in Miami, FL and Detroit, MI. From this sample of 200 dyads, a subsample of participants and their main partner (~N=40 dyads/n=80 men) will be interviewed, individually and simultaneously, about their unsuccessful attempts to obtain PrEP and the factors associated with these unsuccessful attempts. Our purposive English or Spanish speaking sample will be drawn from targeted electronic advertisements on a range of social media used by MSM. The advertisements will reflect the diversity of the MSM populations in these two cities and who are most severely impacted by HIV (e.g., Black and Hispanic MSM, younger MSM). To address how different levels of factors may impact PrEP uptake among male couples, our study will be guided by Bronfenbrenner's Ecological Model paired with advanced analytic methods. Our project's overall aim is to examine how individual, dyadic, social network and community factors shape support, willingness, current use, and unsuccessful attempts to adopt PrEP among a diverse sample of 100 concordantly HIV-negative and 100 HIV-discordant male couples from two U.S. cities that lack substantial PrEP resources. The proposed findings will highlight which hierarchal factors and actor-partner effects reinforce PrEP support, willingness, current use, and unsuccessful attempts among at-risk male couples. Findings from this novel, efficient study will help inform the development of effective PrEP messaging for male couples and will also shape the development of future dyadic interventions.