Background: Among inmate populations in South Africa, there is limited information on how marital status impact heterosexual of the human immunodeficiency virus (HIV) transmission. One reason for the heightened number of HIV cases in South Africa is due to risk associated with heterosexual transmission. Objective: The present study explores the relationship between sexual behaviors of inmates; self-reported marital status, and locality of where inmates were incarcerated. Methods: This cross-sectional descriptive study of inmates, formed part of a larger longitudinal investigation of South African inmates. The study sites were four prisons in KwaZulu-Natal and Mpumalanga provinces. Odds ratios were used to examine associations between the dichotomized correlates and the outcome measure. Results: About 357 male inmates participated in the study. The majority of participants were Nguni speakers (96%). For the entire sample, two outcomes (being responsible for a pregnancy and willingness to have a HIV test) achieve a statistical significance level of P < 0.003. Married inmates in the KwaZulu-Natal prisons were 3 times more likely to have heard of sexually transmitted infections (STIs) prior (P < 0.007) and 2.49 more likely to have had a STI than non-married inmates. Conclusion: Findings form this study highlights prior marital status and sexual risk behavior amongst inmates. This highlights the importance of understanding the relationship between socio-demographic variables, cultural influences, and ethnic practic es and its implications for HIV/STI prevention among inmate populations.