Purpose: The study investigates how various accountability contexts--including states, local boards, districts, school site councils, parent associations, and teachers--affect the ability of principals to influence instructional and supervisory decisions in their schools. Data: Data for the analysis come from 1999-2000 Schools and Staffing Survey responses of 8,524 elementary, middle, and high school principals in low-, moderate-, and high-control states. Principals responded to queries regarding their personal influence and the influence of various other policy actors on decisions in the instructional and supervisory domains in the principals' schools. Analysis: To examine variation in principal influence within and between states, the study uses hierarchical linear modeling as its primary analytic technique. Findings: Results indicate that the various accountability contexts differentially affect principals' influence, which also vary by domain, extent of state control, and region. Implications for Practice: Principals' influence in both the supervisory and instructional domains is strongly related to that of teachers' active participation in decision making, suggesting the benefits of mutuality in school leadership. Implications for Research: How do state accountability systems differ in relation to improving student achievement? How has an accountability-influenced learning process led to the reculturing of a school district and its schools? (Contains 6 tables.)