To identify how high school assistant principals in large suburban schools serve as instructional leaders and how they develop these skills, this research utilized a multiple-case study design, followed by a cross-case analysis of the data. This research explores the instructional leadership of three female comprehensive high school assistant principals who are employed in the same Northern California school district. Each case was developed with the use of interviews, observation and document analysis. Included in each case is a description of the assistant principal's instructional job responsibilities, how they develop their instructional leadership and obtain opportunities to function in instructional leadership roles. This research found several main themes. They include that the theoretical model for Hallinger's Principals Instructional Management Rating Scale did not work in regards to assistant principals, they were found to serve not in the role of leader, but more in the role of facilitator and relationship builders, the role of the assistant principal has not evolved over the past century, they are constrained by the political dynamics of their school structure which leaves them as marginalized leaders, they lack opportunities to grow as instructional leaders due to opportunities for professional development and the ambiguity of their role, and female assistant principals may not take the opportunity to serve as a leader since this may not be perceived natural due to their gender association. [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.]