Assistant principals are important school leaders who serve their school communities in a number of ways. This study focused on Upwardly Mobile and Career Assistant Principals, who either serve for a short period of time before becoming principals or for the duration of their administrative careers, respectively (Marshall et al., 1990). The intent of this study was to fill a gap in the literature with respect to the current understanding of assistant principals and their traits, experiences, and socialization. A panel of 13 assistant principal participants from the state of Indiana took part in a modified Delphi methodology with three rounds seeking to better understand what roles assistant principals are responsible for, whether those roles impacted their longevity, whether their uniqueness helped them to flourish in their roles, and whether the role of assistant principal prepared these individuals for sustained leadership success and job satisfaction throughout their careers. Four themes were compiled from the three Delphi rounds that were used to provide suggestions to aspiring and practicing assistant principals, other school leaders, and the higher education faculty members that design assistant principal preparation programs. Those themes include: (1) Assistant principals functioned within several types of administrative teams, including teams within their buildings and within their districts. (2) Two key elements, including factors from Herzberg's Two-Factor Hygiene and Motivation Theory and other unique factors, played a role in assistant principal longevity. (3) Assistant principals' roles, experiences, and unique traits provided opportunities to expand their leadership. (4) The transition into an assistant principalship is an important time of growth and socialization for new administrators. [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.]