This paper discusses a dispute concerning the ethics of research on preventing the perinatal transmission of HIV in developing nations. Critics of this research argue that it is unethical because it denies a proven treatment to placebo-control groups. Since studies conducted in developed nations would not deny this treatment to subjects, the critics maintain that these experiments manifest a double standard for ethical research and that a single standard of ethics should apply to all research on human subjects. Proponents of the research, however, argue that these charges fail to understand the ethical complexities of research in developing nations, and that study designs can vary according to the social, economic, and scientific conditions of research. This essay explores some of the ethical issues raised by this controversial case in order to shed some light on the deeper, meta-ethical questions. The paper argues that standards of ethical research on human subjects are universal but not absolute: there are some general ethical principles that apply to all cases of human subjects research but the application of these principles must take into account factors inherent in particular situations.