The current study from the National Center on School Choice contributes to the research by exploring the factors that affect principals' perceptions of charter school competition and the extent to which their leadership behavior may change in response. Central research questions of the study were: (1) How do principals perceive the competition produced by charter schools, and how do their perceptions vary among private, magnet, and traditional public schools?; (2) What factors affect principals' perceptions of charter competition?; and (3) What is the relationship between charter competition and principals' leadership behavior? The study relied on a matched convenience sample of schools and their principals. The final sample comprised 101 traditional public schools, 22 magnet schools, and 15 private schools. Key findings include: (1) Principals perceived little competition from charter schools affecting either their financial resources or their recruitment of teachers and students; (2) When a school has more charter schools in close proximity, principals perceived a more negative effect of charter schools on their ability to attract and retain teachers and students; and (3) Principals' perception of charter school competition was not related to the ways they spend their time. (Contains 2 footnotes.) [This brief summarizes a chapter in Berends, M., Cannata, M., & Goldring, E. B. (Eds.). (2011). "School choice and school improvement." Cambridge, MA: Harvard Education Press.]