For the past several decades, financial uncertainty, changes in health care delivery and reimbursement, and changing workforce needs have prompted medical schools to continually refine their appointment and tenure policies. Studies during the past 30 years have examined the nature of these faculty appointment and tenure policies in U.S. medical schools, and in this article the authors present data from a 2005 survey on faculty personnel policies to extend this analysis. For both basic science and clinical faculty in U.S. medical schools, the authors describe tenure systems, trends in the number and percentage of full-time faculty on tenure-eligible tracks, the financial guarantee of tenure, and probationary period lengths. They review the status of flexible policies and highlight two current faculty policy changes that many institutions have made or are actively contemplating: the recognition of interdisciplinary and team science, and a broadening view of scholarship. Results show that although tenure systems remain well established in medical schools, the proportion of faculty on tenured or tenure-eligible tracks has continued to decline over time. Changes in the financial guarantee associated with tenure have transformed the fundamental concept of tenure at many medical schools, and the percentage of schools that have lengthened the probationary period for tenure-track faculty has steadily increased during the past 25 years. Tenure-clock-stopping policies and part-time tenure policies continue to exist at medical schools, though results indicate low faculty use of the policies, suggesting a disconnect between policy and practice.