Medical graduates in 1983 were in preclinical training when the Graduate Medical Education National Advisory Committee forecast a surplus of 70,000 physicians by 1990. Among the problems identified was the nuclear role of medical schools in affecting specialty choices. To understand this role further, the current study determined the stability and evolution of specialty preferences between the time of the Medical College Admission Test and the senior year of medical school. The study included 10,321 US medical school graduates in 1983. Eighty percent changed their specialty preference during this interval, demonstrating the substantial effects that medical schools have on specialty selection. The stability of early preferences ranged from 41% to 1%. Interest in primary care specialties declined among both men and women; interest in specialty care and supporting services increased during this five-year longitudinal study. These findings parallel shifts away from primary care among US medical school graduates in 1978 and 1983.