School administrators rank second behind teachers in impact on student achievement. New high school assistant principals need to be prepared for the challenge of transitioning from a teaching position to that of a school leader in Pennsylvania. Aspiring administrators typically attend a principal preparation program, while new administrators are required to attend ongoing professional development in the first few years on the job. However, there may be additional transitional supports needed for new administrators to be successful. The purpose of this phenomenological study is to examine the lived experience of the new high school assistant principal in the state of Pennsylvania, while identifying transitional supports that were present and which may have been beneficial to the new administrator if present. Audiotaped, semistructured interviews and document analysis will be conducted. Data analysis consists of the identification of themes using color-coding techniques. Key research questions surround the shared lived experience of transitioning into a new high school assistant principal position in the state of Pennsylvania, as well as the transitional supports which new administrators perceive to be the most helpful while making the transition. Results of this study will inform pre-service training programs, as well as ongoing professional development, school districts, and universities. [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.]