There has been much discussion about the declining number of physician-scientists, and their potential impact on biomedical research and discovery. However, less attention has been paid to the fact that women are underrepresented in this area. Remarkably, as a woman physician-scientist, and director of the Harvard-MIT MD-PhD Program, I had never given it much thought. However, after talking with students and colleagues, I am convinced that women find physician-scientist careers much less attractive than do men. The initial ‘pipeline’only carries a trickle, and it leaks. As Charles Vest, the President of MIT, wrote in his preface to the landmark 1999 report on women faculty1,“I have always believed that contemporary gender discrimination within universities is part reality and part perception. True, but I now understand that reality is by far the greater part of the balance.” The bottom line is that there are valid reasons for women opting out.