Physicians often change their specialty over time. A study looked at medical school graduates from 1960, 1964, and 1968 to see how many switched specialties by 1971 and 1976. Out of 2,046 doctors, 16% changed their specialty. The rate varied by graduation year, with 8% for 1960, 11% for 1964, and 29% for 1968. Most changes were from one specialty to another or back to a different residency. About 22% switched from one residency to another specialty. Among primary care doctors, 16% changed their specialty during the study period. This information is important for planning how many doctors are needed in each specialty.