While early studies tended to find positive correlations between economic resources, education and HIV infection, as the epidemic has progressed, it has increasingly been assumed that this relationship is changing. But what is really known about the degree, type and dynamics of the influence of socioeconomic factors on rates of HIV transmission in different settings and at various stages of the AIDS epidemic? This brief highlights the key findings of a review of studies that sought to address this question. In most countries, relatively rich and better educated men and women have higher rates of partner change because they have greater personal autonomy and spatial mobility. Although the richer and better educated are likely to have better access to reproductive health care, condom use is generally low in Africa and other parts of the developing world. Pre-existing sexual behaviour patterns therefore make the richer and the better educated more vulnerable to HIV infection, especially in the early stages of the epidemic, when information about the virus and how to protect oneself is usually low. At a later stage, however, it has been argued that individuals with higher socioeconomic status tend to adopt safer sexual practices, once the effects of AIDS-related morbidity and mortality become more apparent, adding greater credibility to HIV prevention messages.