In May 2000, a General Accounting Office (GAO) report revealed that although women are now participating in clinical trials in numbers proportionate to their numbers in the general population, data collected in these trials are not routinely analyzed by sex.[1] Without such sex analysis, clinically relevant information about potentially lifesaving treatments could be lost. In July 2001, the Society for Women's Health Research convened a workshop to address strategies for conducting subgroup analyses to detect sex differences. Workshop participants concluded that understanding sex differences will enable medical researchers to design healthcare interventions for both men and women more effectively and that one can plan for and conduct sex analysis without compromising the quality of the study or making the study prohibitively expensive.