Developing excellent principals who can set direction, develop people, redesign organizations, and lead instruction requires a system of high-quality preparation and professional development. This paper summarizes the elements of high-quality principal preparation and professional development programs that have been associated with positive school outcomes, ranging from student achievement, to staff and student perceptions of school climate, to principal efficacy and retention. To illustrate how these elements work together to develop strong principals, the paper also includes descriptions of four programs that have been found to produce effective principals.