While prior studies have identified a number of factors individually related to physician practice in rural areas, little information is available regarding the relative importance of these factors or their relationship to rural retention. Extensive data previously collected from the Jefferson Longitudinal Study were analyzed for 1972 to 1991 graduates of Jefferson Medical College practicing in Pennsylvania in 1996, as were recent self-reported perceptions of Jefferson Medical College graduates in rural practice. Rural background was overwhelmingly the most important independent predictor of rural practice, and freshman plans to enter family practice was the only other independent predictor. No other variable, including curriculum or debt, added significantly to the likelihood of rural practice. None of these variables, however, including rural background, was predictive of retention, which appeared to be more related to practice issues such as income and workload. These results suggest that increasing the number of physicians who grew up in rural areas is not only the most effective way to increase the number of rural physicians, but any policy that does not include this may be unsuccessful.