Assistant principals typically begin their careers as teachers and transition to the role of assistant principal after completing a certification program that characteristically focuses on the principalship. Once they move into the role of assistant principal, many feel unprepared as the job responsibilities, assigned by the principal, usually revolve around the three Bs--books, butts, and buses. As they learn and master the role of assistant principal, they face the probability of being tapped to serve as a principal which in turn requires its own skillset for success. The goal of this qualitative study was to investigate assistant principals' self-perception of their professional development and mentoring experiences. Personal interviews were conducted with 10 assistant principals, in one suburban district in the southeastern area of the United States, to identify components of professional development and mentoring experiences that were beneficial to their improvement as an assistant principal and would prepare them for a principalship. Results of this study revealed two prevalent themes representing their beliefs: challenges and support. Assistant principals opined there are so many challenges to their job that support from professional development and mentors is critical. Recommendations for improvement to professional development and mentoring experiences were offered including format, topics, and timing. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]