The ethical implications of research into HIV infection and AIDS merit attention in their own right, but of related concern are the ethical implications of HlV infection and AIDS research that investigators in sponsoring international agencies and countries, principally in the developed world, plan and execute in host countries that are principally in the developing world. HlV/AIDS is now a universal phenomenon, but its burden, until recently most profoundly felt in countries of sub-Saharan Africa, especially East Africa, is spreading to countries of Asia that, like those of Africa, are ill-equipped to cope with its personal and economic effects. Within the general area of research with human subjects, concerns arise about how research on HlV infection and AIDS in particular, has affected popular understanding of the character of medical and wider health research. Trans-national research raises questions about the ethical sensitivities that have to be applied when investigators propose research studies on human subjects to be conducted in cultures with which they are unfamiliar, and when investigators from countries with relatively affluent economies intend to develop and implement. research among relatively resource-poor populations, in other countries. Countries with relative wealth often contain impoverished populations, among which HlV infection and AIDS may have an above-average incidence, but the focus of this paper will be on low-income populations in countries other than the investigators' own.