Differences in income between male and female academic physicians are well known, but differences for community physicians and career differences in income have not been quantified. We used earnings data from 80,342 full-time US physicians to estimate career differences in income between men and women. The differences in annual income between male and female physicians that we observed in our simulations increased most rapidly during the initial years of practice. Over the course of a simulated forty-year career, male physicians earned an average adjusted gross income of $8,307,327 compared with an average of $6,263,446 for female physicians-an absolute adjusted difference of $2,043,881 and relative difference of 24.6 percent. Gender differences in career earnings were largest for surgical specialists ($2.5 million difference), followed by nonsurgical specialists ($1.6 million difference) and primary care physicians ($0.9 million difference). These findings imply that over the course of a career, female US physicians were estimated to earn, on average, more than $2 million less than male US physicians after adjustment for factors that may otherwise explain observed differences in income, such as hours worked, clinical revenue, practice type, and specialty.