Our society has long sanctioned, at least tacitly, a conflict of interest in medical practice and research as an unavoidable consequence of the different interests of the participants in health care: the physician or clinical researcher, the patient or research subject, insurance companies or research sponsors, the government, and society as a whole. This multidisciplinary effort draws from philosophy, medicine, law, economics and public policy to identify and categorize conflicts of interest in medical practice and clinical research, and, where possible, to offer a mechanism for resolving them. Part I reviews the theoretical background, including basic concepts and analytical frameworks. The second part discusses two topics prominent in current health care policy debates--self-referral and financial incentives to limit care. Part III examines conflicts of interest generated by pharmaceutical industry involvement in clinical practice and research. The final section deals with clinical research in several contexts, including institutional review boards, clinical trials, research agreements between the government and private researchers, brokerage of research subjects by contract research organizations, and cost-effectiveness studies.