The maternal-fetal HIV transmission trials, conducted in developing countries in the 1990s, undoubtedly generated one of the most intense, high profile controversies in international research ethics. They sparked off a prolonged acrimonious and public debate and deeply divided the scientific community. They also provided an impetus for the revision of the Declaration of Helsinki--the most widely known guideline for international research. In this paper, I provide a brief summary of the context, outline the arguments for and against the controversial use of placebo controls, and focus on particular areas that I believe merit further discussion or clarification. On balance, I argue that the researchers failed in their duties to protect the best interests of their research subjects, and to promote distributive justice. I discuss the difficulties of obtaining valid consent in this research context, and argue that it is unethical to inform women of their HIV status without at least offering them prophylactic treatment for their unborn children. A global view of justice, which endorses international equity, cannot be squared with international research guidelines that allow 'local conditions' to define the scope of duty to the control group. Finally, I suggest that the heated debate reflects a tension, if not an outright war, between two conflicting meta-ethical systems, or incommensurable paradigms, that underpin scientific research involving human subjects.