Women now constitute 43% of US medical students, 37% of residents, and 27% of full-time medical school faculty. Less than 11% of women faculty are full professors, however, compared to 31% of men, and these proportions haven't changed in more than 15 years. Since the proportion of women reaching the top ranks remains relatively low, the pool of women available for leadership positions in academic medicine is still small. This review article first summarizes recent data on women's representation in academic medicine and then discusses why they are not succeeding at the same pace as men. Reasons include a complex combination of women's choices, sexism, cultural stereotypes, constraints in combining family responsibilities with professional opportunities, and lack of effective mentoring. Multiple approaches are required to overcome these "cumulative disadvantages," among them improving the gender climate at academic medical centers; the mentoring of women faculty, residents, and students; and skill-building opportunities for women.