Purpose: Knowledge about principals' leadership roles in charter schools' success has become more important as the number of charter schools increases and as we have learned more about the influence of principal leadership on school effectiveness. To contribute to the limited empirical literature on the principal labor market, this study explores the reasons for the disparity of turnover rates between charter school principals and their counterparts in traditional public schools (TPSs). It focuses on the differential distributions of observable factors, including principal characteristics, principal leadership practices, school contexts, and working conditions. It also examines how the associations between these observables and the likelihood of principal turnover differ between these two types of schools. Research Methods/Approach: This study uses data on a nationally representative sample of principals from the Schools and Staffing Survey in the 2007-2008 school year and its following-year Principal Follow-up Survey. The main analytic strategies include logit models and the Fairlie nonlinear decomposition technique. Findings: A statistically significant difference in charter-TPS principal turnover rates was confirmed. The explanatory variables collectively explained about 49% of the charter-TPS turnover gap: Principal characteristics explained 3%, principal leadership quality explained 4%, school contexts explained 2%, and working conditions explained 28%. Moreover, relative to TPS peers, three factors have stronger associations with the likelihood of charter school principal turnover: principal leadership quality, barriers to the dismissal of poor-performing or incompetent teachers, and salary. Implications for Research and Practice: This is one of first few studies that empirically explore the charter school principal workforce and labor market movements. Findings are practically informative for retaining principals in charter schools.