In 1999, Médecins Sans Frontières (MSF) set out to explore and demonstrate the feasibility of preventing and treating HIV/AIDS in a so-called resource-poor, economically and socially disadvantaged setting. The first MSF mission to incorporate antiretroviral (ARV) treatment into its HIV-AIDS-oriented medical program was undertaken in Bangkok. The second project was launched in Khayelitsha where MSF has been providing ARV treatment for persons with HIV/AIDS since May 2001. Khayelitsha is an enclave of some 500,000 inhabitants, most of whom live in corrugated-iron shacks, without running water or electricity. Unemployment is extremely high; crime and violence (including robbery, domestic violence, rape, and murder) are rampant. The general prevalence of HIV/AIDS is 26%, measured among pregnant women. The tuberculosis incidence rate is one of the world's highest for open-space sites (1,380/100,000). Unsurprisingly, TB/HIV coinfection is very high too: 63% of those with TB are also infected with HIV. Renée C. Fox made two field research trips to the Khayelitsha HIV/AIDS project in connection with her ongoing sociological study of Médecins Sans Frontières, which centers on moral dilemmas associated with medical humanitarian action. Her research has been supported by grants from The Acadia Institute, the Honorable Walter H. Annenberg Chair in the Social Sciences Research Fund at the University of Pennsylvania, and the Andrew W. Mellon Foundation in the United States, and from the Nuffield Foundation in the United Kingdom. We express our gratitude to Nicholas A. Christakis, M.D., the late Willy De Craemer, Ph.D., Robert L. Klitzman, M.D., and especially to Judith P. Swazey, Ph.D., for their astutely critical and encouragingly helpful comments on earlier drafts of this article. Disclaimer: Patients' consent and permission to publish are not required, because no research was conducted on patients, and the cases described in the article do not reveal the patients' identity or breach their privacy.