Protection of human subjects from investigators' conflicts of interest is critical to the integrity of clinical investigation. Personal financial conflicts of interest are addressed by university policies, professional society guidelines, public standards, and government regulation, but "intrinsic conflict of interest"--conflicts of interest inherent in all clinical research--have received relatively less attention. Such conflicts arise in all clinical research endeavors as a result of the tension among professionals' responsibilities to their research and to their patients and both academic and financial incentives. These conflicts should be disclosed to research subjects and managed as assiduously as are financial conflicts of interest.