The careers of MBAs from a top US business school are studied to understand how career dynamics differ by gender. Although male and female MBAs have nearly identical earnings at the outset of their careers, their earnings soon diverge, with the male earnings advantage reaching almost 60 log points a decade after MBA completion. Three proximate factors account for the large and rising gender gap in earnings: differences in training prior to MBA graduation, differences in career interruptions, and differences in weekly hours. The greater career discontinuity and shorter work hours for female MBAs are largely associated with motherhood. (JEL J16, J22, J31, J44)