The U.S. Code of Federal Regulations governing federally funded research on human subjects assumes that harmful research is sometimes morally justifiable because the beneficiaries of that research share a particular vulnerability with its subjects. In this article, I argue against this assumption, which occurs in every subpart of the Code of Federal Regulations that deals with specific vulnerable populations . I argue that shared vulnerability is no exception to the general principle that harming one person in order to benefit another (...) is no more justifiable if the two people have traits in common. Further, shared vulnerability is not a reasonable proxy for any morally relevant desideratum of research, in particular the desire to benefit the worst off, the desire to avoid exploitation, and the desire to use vulnerable populations in research only when necessary. (shrink)