Background. There are few data on HIV prevalence and risk factors among inner-city homeless and marginally housed individuals in South Africa. Methods. We recruited 136 adults from a Johannesburg inner-city homeless clinic; mean age was 32.4 years, 129 (95%) were male, and 90 (66%) were of South African nationality. Participants were tested for HIV and answered a short demographic survey. Descriptive statistics and uni- and multivariate regression analyses were used for data analysis. Results. The HIV prevalence in the cohort was 23.5%. Transactional sex, relationship status, number of concurrent sexual partners, condom usage and history of previously treated sexually transmitted infections (STIs), living on the street, the use of alcohol or drugs, and previous exposure to voluntary counselling and testing (VCT), were not significant risk factors for HIV-positivity. Statistically significant HIV risk factors on multivariate analysis included the presence of an STI (odds ratio (OR) 5.6; p