Despite millions of dollars spent on reform efforts, effective and sustainable improvement still eludes schools. The appropriate development of the professional learning community model, including five key dimensions, provides a structure for educational institutions to bring about sustainable improvements in student achievement. If principals do not understand how to effectively implement a proven strategy, such as the professional learning community, student achievement may not rise. The result of not reaching student achievement benchmarks is that schools will continue to face punitive accountability policies, principals and staffs will face job loss, and schools may be closed or taken over by the state. The purpose of this qualitative case study was to examine teachers' perceptions of principals' roles and actions in successful professional learning communities within the five dimensions of a professional learning community as defined by Hord. Teachers were recruited from schools from within one school district in the Southeastern United States. Teachers were chosen to interview if they were active in a successful school professional learning community. The data gathered provided themes that addressed the central research question regarding what roles and actions school principals engage in to support successful PLCs. Those themes include the following actions principals must take: (1) use intentional planning over time, (2) present data in a frequent manner, (3) present reflective questioning with time for rich discussion frequently, (4) empower teachers to make decisions and direct responsibility towards the whole staff, (5) foster the ability of the staff to analyze their own data, (6) encourage and promote teachers to review student work through a formalized process, (7) model providing constructive feedback and likewise encourage teachers to practice giving and receiving constructive feedback, (8) pay close attention to their own body language, tone of voice, and word choice, and (9) provide clear purpose with exemplars on a consistent basis. Recommendations for future research include modification of the qualitative study as it stands currently and opportunities for future research using a mixed design. Future researchers, regardless of the design, may explore a wider variety of participants for whom to gather perceptions. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]