The U.S. HIV/AIDS epidemic disproportionately impacts lower-income populations. We conducted a cross-sectional study of heterosexually active adults (N = 1076) in areas with high poverty and HIV/AIDS rates in South Florida in 2007. Using venue-based sampling, anonymous interviews and HIV tests were conducted at randomly selected venues (primarily retail businesses not associated with risk behaviors). The sample's HIV infection rate was 7.1%. Half (52.2%) of the infections were previously undiagnosed. Our findings underscore the impact of social and environmental factors on HIV risk, as well as the need to increase and optimize HIV testing and other prevention services.