In-depth Understanding of HIV Risk Behavior among Men Who Have Sex With Men in Sub-Saharan Africa: Secondary Analysis of HPTN 075 Data - The aim of this project is to use the rich data collected for the HIV Prevention Trials Network (HPTN) 075 study to expand our understanding of the sexual behavior and HIV risk practices of men who have sex with men (MSM) in sub-Saharan Africa (SSA). HPTN 075 was a vanguard study with the primary aim to assess the feasibility of recruiting and retaining 400 men who have sex with men (MSM) in sub-Saharan Africa (SSA) in preparation for further HIV prevention studies. This aim was successfully addressed in a multinational, prospective biobehavioral cohort with five study visits over a one-year follow-up period. Each study visit included behavioral and clinical assessments. The study was conducted from 2015 to 2017 in four sites: Blantyre in Malawi, Kisumu in Kenya, and Cape Town and Soweto in South Africa. HPTN 075 showed an alarmingly high HIV prevalence and incidence among MSM in SSA: 30% of all MSM screened for participation tested HIV positive and an overall incidence was found of 7.0/100 person-years (PY) (95% CI: 4.3, 10.6). Engagement in condomless anal intercourse was the strongest determinant of incidence. The HPTN 075 data set is exceptionally rich: the involvement of four study sites in three countries; detailed assessments of sexual behavior, including on the dyad-level; and the longitudinal design with extensive screening data and five study visits. This rich data will be used to advance our understanding of factors that drive HIV transmission and that need to be addressed to end the HIV epidemic in SSA among MSM and, because of the high prevalence of MSM who also have sex with women, among the general population. The following questions will be answered: (1) Does engagement in condomless anal sex change over the duration of the study due to study-related HIV-risk counseling and improved access to condoms, and which characteristics of the individual (e.g., age, HIV risk perception), the sexual partnership (e.g., age concordance, relationship status), and the sexual encounter (e.g., substance use, place of interaction) are independently associated with condom use? (2) What are the features of sexual interactions that MSM have with women? How do their sexual interactions with men compare to the same-sex interactions of MSM who exclusively have sex with men? (3) What are the characteristics of MSM who engage in transactional sex and how do they differ from men who do not? How are transactional sex interactions different from sexual interactions that are not transactional, and in what way does receiving or providing benefits in exchange for sex affect these differences? (4) What patterns of substance use can be distinguished among MSM in SSA? Are these patterns predictive of HIV incidence and what is the mediating role of condomless receptive or insertive anal sex? (5) Are there differences between countries in sexual behaviors corresponding to the national differences in the legal status and social acceptance of same-sex sexuality? Findings from this study will inform the development of an implementation science study (R01) addressing the needs of MSM in SSA.