This is a qualitative, multi-case study of the reported instructional leadership actions of assistant principals in four Midwestern comprehensive high schools. The study gathered assistant principals descriptions of instructional leadership behaviors they participate in and what hinders their ability to do so. The data was collected using interviews with thirteen assistant principals during the 2008-2009 school year. The main findings of this study are that the assistant principals report they perform a wide number of instructional leadership actions and activities. Yet, according to their reports, the ability to do so varies across assistant principals both across sites and within sites as well. This study concludes that this variability may be impacted by three factors including: (1) the structure of the administrative team, (2) sanctioned choices by the assistant principal, and (3) whether the emphasis of the leadership behavior is on actions that may primarily make an impact on the instructional organization or the culture of the building. This study did not seek to determine the best administrative structure or whether the reported behaviors made an empirically verified impact on instruction. This should be considered limitations of this study. As such, additional research in the area of specific behaviors as well as particular administrative team structures may be beneficial to the work of building principals and assistant principals alike. In addition, the scope of this study was limited to the reported behaviors by the assistant principals at each site. Future research may consider the background, training, experiences of the assistant principals, as well as reports by others in the school, such as teachers and supervisors, to gain a more thorough understanding of the work of the assistant principal. [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.]