This article presents a multivariate analysis of the career preferences of 923 Mexican interns. Such preferences were operationalized along two dimensions: type of activity (general/family practice, primary specialties, or subspecialties) and type of institution (public assistance, social security, or private). There were six independent variables: father's occupation, father's education, type of medical school, place of internship, assimilation to the internship hospital, and perception of the medical labor market. The appearance in recent years of unemployment and underemployment among Mexican physicians made labor market issues particularly salient. Thus the study offered an appropriate occasion to test the relative strengths of alternative explanations of career choice that are based on social mobility, professional socialization, or responses to labor market signals. Results obtained through multiple regression revealed that the most important variable in the determination of activity preference was medical school, although the two social origin variables retained the important role of directing students into different schools. With regard to institution preference, the most important factor was shown to be place of internship, as it interacted with the level of assimilation to the hospital. Although perception of the medical labor market was a significant predictor of both dimensions of career preference, the greater importance of the other variables indicated that, even under extreme conditions of medical unemployment, explanations of career choice must go beyond simple models of rational decisionmaking to include the experiences that socialize future physicians into dominant paradigms about medical practice.