In 2010, Illinois became one of the first states to legislatively require a complete redesign of all its principal preparation programs, with the goal of advancing statewide school improvement through strengthening school leadership. This effort was ambitious and sweeping, calling for radical shifts in previous practice, including: (1) A targeted principal endorsement, instead of a general administrative certificate; (2) Formal partnerships with school districts in preparation program design and delivery; (3) More selective admissions criteria and processes; (4) Focus on leading all students, including students with disabilities, English Language Learners, and early childhood education; (5) Collaborative support for candidates from highly qualified faculty supervisors and mentor principals; and (6) A competency-based internship, with an emphasis on demonstrated leadership skills. For many decades prior to the redesign, principal preparation had typically consisted of administrative courses such as school law, finance, and educational theory, followed by an internship consisting of a set number of hours that were mainly spent shadowing a principal. Programs varied greatly in the quality of both course content and mentoring and generally had few, if any, selection criteria beyond what was required by the college or university. Meanwhile, a growing body of research evidence indicated that principals play a critical role in improving student performance and leading effective schools. This research identified the importance of principals as effective instructional leaders rather than simply efficient building managers, and identified key components of effective principal preparation programs, including: targeted recruitment and selection, a rigorous curriculum focused on instruction and school improvement; integration of coursework and fieldwork; and robust, sustained internships that allow candidates to gain leadership experience working with an expert mentor. As a result, traditional principal preparation began to be perceived as providing inadequate training, and principal preparation programs became the target of intense scrutiny. For the past two years, the authors have studied the implementation of Illinois' new principal preparation programs and the changes that have occurred as a result of the new policy. In this policy brief, they highlight key findings and implications from the second phase of the study. The full findings and analysis are presented in the final report. [For the final report, "Navigating the Shift to Intensive Principal Preparation in Illinois: An In-Depth Look at Stakeholder Perspectives. Policy Research: IERC 2016-2," see ED567016.]