There is a striking variation in the prevalence of the human immunodeficiency virus (HIV) among countries and regions of the world, with a distinct geographical pattern. This paper explores the link between income inequality and HIV. It presents empirical evidence—a meta-study and additional cross-country regression results—that clearly support the argument that such a link exists. The interpretation of this link is an open issue. Four different hypotheses are discussed, each one pointing out a transit route from income inequality to HIV. The paper presents preliminary evidence on these routes and identifies potential areas for future research.