While many factors have been proposed to explain the specialty choice decisions of medical students, little has been reported on the reasons for change of career choice during medical school. The purpose of this study was to determine why medical students switched from primary care to nonprimary care as a career choice and why others changed from nonprimary care to primary care as a specialty preference. Of the 1981-1990 graduates of Wright State University School of Medicine (n = 832) investigated, 217 switched preference during medical school (53 to primary care, 164 to nonprimary care). Reasons relating to the medical school experience were more influential than personal or societal reasons, more so for students changing to nonprimary care than for those changing to primary care. Increased awareness of specialties and positive clinical experience in chosen specialties were indicated by 76% and 70% of those who switched. Among reasons selected less frequently, content and emphasis of the curriculum (19% versus 7%) and location of residency (17% versus 6%) were more likely to be cited by those switching to primary care than by those who switched to nonprimary care, while better financial opportunities were more important for those who switched to nonprimary care (17% versus 4%).