There is increasing concern among many in the medical arena about the extent to which the effects of treatment, either good or bad, apply to specific subgroups of individuals. Women comprise one of the most frequently considered 'subgroups' of patients. In the 1980s, much political attention was focused on concerns about equity in the research enterprise. In this paper, we briefly describe the statutory approaches to achieving equity in research, beginning with The NIH Revitalization Act of 1993. We go on to describe clinical, methodological and political factors affecting these discussions. We conclude that the controversy over the inclusion of women in clinical trials probably stems, in part, from theoretical concerns about gender differences in treatment effects and, in part, by legitimate fears of exposing fetuses to investigational drugs. However, we believe that the broader issue centres on biological factors, possibly defined by genes or gene expression, that may directly or indirectly modify the effect of specific treatments on specific individuals.