Relatively little consideration has heretofore been given to the interaction between Western clinical research ethics and non-Western ethical expectations. How should any conflict that might arise when a biomedical investigator and a research subject come from different cultural settings and have different ethical expectations be addressed? Which ethics should govern such trans-cultural clinical research? The answers to these questions are of increasing importance because many countries of the developing world are presently sites of field testing of biomedical agents sponsored and administered by countries of the developed world, especially in the context of the AIDS pandemic. Drawing mainly on examples from Asian medical systems and settings, I elucidate four possible ethical models to guide the conduct of transcultural biomedical research. Two assume that research ethics are culturally relative and two assume that a unified, universalistic conceptualization of research ethics is possible. All four, however, are problematic and are to a large extent deficient. The cause of the deficiencies of these models lies, I argue, in the way that ethics are ordinarily conceived. The proper approach to ethical conflict recognizes that culture shapes (1) the content of ethical precepts, (2) the form of ethical precepts, and (3) the way ethical conflict is handled. Medical ethics may be viewed in cross-cultural perspective as a form of 'local knowledge', and any differences in such knowledge between cultures--since such differences will not conveniently disappear--must be engaged and negotiated.