Numerous studies have demonstrated differences among students regarding their preference of a medical specialty. The goal of the present research was to develop a model for the selection of a primary care specialty (ie, family practice, general internal medicine, medicine/pediatrics, and general pediatrics). A self-administered questionnaire was mailed to 822 first-year through fourth-year medical students at the University of Michigan Medical School in Ann Arbor. Students listed their first preference for medical specialty, anticipated income and work hours, and the influence of attitudinal and social factors on their preference. A total of 645 (78.5%) students responded. Average age was 25; 58% were male, and 77% resided in Michigan. Overall, 34.3% of the medical students who responded to the questionnaire expressed a preference for a surgical specialty; 27.3%, primary care; 19.9%, a hospital-based practice; and 18.5%, nonprimary care and non-hospital based practice. A multiple logistic regression model developed on preference for a primary care specialty achieved a classification accuracy of 82%. The most important factors influencing specialty preference were sex, expected income, attitudes about general medicine issues, attitudes about surgery, and the influence of other people. No single factor dominates a student's preference for primary care. Students preferring primary care were most strongly influenced by their perceptions of practice variations. Students preferring nonprimary care specialties were more interested in income, prestige, and hospital-based practice. Medical school faculty had no significant impact on the preferences of either group of students.