This article explores the practices of charter school authorizes in Arizona and Michigan, including the two Arizona state boards and Central Michigan University (CMU). The author focuses on the role of authorizers in authorizing new schools, overseeing operating schools and holding them accountable, and providing technical assistance. When this study ended, CMU had developed a larger and more bureaucratic organization than the Arizona boards and tended to focus more on issues of compliance. An examination of the isomorphic pressures, or pressures to become similar to preexisting organizations (such as districts and state education agencies), helps to explain why authorizers in each state have taken rather different directions.