This paper reports on an exploratory study investigating links between sexual health and social capital in a South African mining community. In this study, social capital is defined in terms of people's membership of voluntary community organizations (e.g. church, residents' associations, youth groups). Using biomedical and social survey data from a stratified random sample of 1,211 Carletonville residents, we tested the hypothesis that organizational members were less likely to have HIV. Multivariate analysis of variance sought to identify significant associations between nine organizational memberships and HIV infection, as well as three risk factors for infection (casual partners, condom use with casual partners and alcohol consumption). Analysis yielded a range of significant results, but findings varied across age and gender, and were not all in the hypothesized direction. For example, young men and young women who belonged to sports clubs were less likely to be HIV-positive, and young women who belonged to sports clubs were more likely to use condoms with casual partners than non-members. Amongst members of stokvels (voluntary savings clubs accompanied by social festivities), however, young men were more likely to be HIV-positive, women of all ages were more likely to have a casual partner, and both young men and young women were more likely to drink alcohol than non-members. While our exploratory study has produced sufficient evidence to justify the need for further research in this area, it also highlights that the interface between HIV infection and social capital is a complex area that defies easy generalization.