The number of faculty in academic medical centers, and clinical enterprises in particular, has expanded profoundly over the past several decades. During this expansion, the prevalence of tenure systems and the actual numbers and proportions of tenured positions in U.S. medical schools have garnered much attention. Some commentators have remarked that the system of tenure is vanishing from schools and that the opportunity for tenure-track appointments is declining, especially for clinical faculty. This Analysis in Brief presents data on the current status of tenure systems, the changing distribution of clinical M.D. faculty on tenure-eligible tracks, and trends in numbers of these positions over the past quarter-century.