In the last 25 years, human immunodeficiency virus (HIV) has become the leading infectious killer of adults globally, with an estimated 44 million people infected with the virus worldwide. Most of these individuals live in poor regions of the world, particularly sub-Saharan Africa. Although a great deal of work has been done in identifying and treating individuals with the disease, there has been little action to date to address the complex socioeconomic factors that lie at the heart of this global pandemic. Understanding and responding to such factors is of paramount importance if HIV infection is to be managed in a meaningful way. This article explores the social context of people living with HIV in three different geographic and epidemiologic settings and highlights the social factors that shape and define an individual's risk of acquiring HIV. It also discusses unique programs aimed at addressing the complex realities of the world in which HIV thrives. These programs can act as models of HIV prevention and treatment. © 2008 New York Academy of Sciences.