Mimiaga MJ, Hughto JMW, Klasko-Foster, et al. - Given the findings from cross-sectional studies of male sex workers (MSW) suggesting correlation of co-occurring epidemics or a “syndemic” (co-occurring epidemics) of psychosocial problems with an increased vulnerability to HIV acquisition/transmission by elevated sexual risk, researchers here investigated how a syndemic of six psychosocial problems lead to additive risk for condomless anal sex (CAS) with male clients in a multicity, longitudinal cohort of MSW. Between 2015 and 2017, behavioral/psychosocial surveys were completed by 100 MSW from Boston, MA and Providence, RI at baseline, 6 months, and 12 months. Analyses revealed higher likelihood of psychosocial problems and engaging in HIV sexual risk with male clients among internet escorts and street-based MSW. This prospective cohort of MSW indicated additive predictive value of the accumulation of psychosocial problems for CAS with male clients. In the United States, the specification of psychosocial problems confers distinct treatment targets for HIV prevention among MSW.