As a consequence of recent changes, health research policies in the United States mandate the inclusion of women and members of racial and ethnic minority groups as experimental subjects in biomedical research. This article analyzes debates that underlie these policies and that concern the medical management of bodies, groups, identities and differences. Much of the uncertainty surrounding these new policies reflects the fact that researchers, physicians, policy makers and health advocates have adopted competing, and often murky, understandings of the nature (...) of sex, gender, racial and ethnic differences, and of the relation of the biological to the social in the manifestation of bodily illness. (shrink)