Research focused on school improvement points to the principal as one of the decisive factors needed to sustain school success and increase student achievement (Cowie & Crawford, 2007; Duke, Grogan, Tucker, & Heinecke, 2003; Tucker, Henig, & Salmonowicz, 2005). Despite the demonstrated importance of principal leadership, large school districts often pay scant attention to the implementation of programs of leadership development designed to build principal leadership capacity (Grissom, 2010). The complexities and competing demands often present within large school districts hinder leadership development programs (Grissom, 2010). This dearth of comprehensive leadership development exacerbates the difficult task most principals face when assuming their leadership position. Given the leadership challenge that confronts principals, this study attempts to ascertain the existence and effectiveness of leadership development programs aimed at building principal leadership capacity. Day (2001) defined leadership development as the process of expanding the collective capacity of organizational members to engage effectively in leadership roles and processes. Davis (2003) found that programs of leadership development strengthened an individual's ability to establish a clear vision, develop goals, and motivate others to subscribe to formulated visions and goals. Superintendents serve as the linchpin for the implementation, sustained focus, and ultimate success of leadership development efforts. The most successful superintendents embrace major challenges and seek to develop the latent capabilities currently present within their organizations (Kowalski, 2012). A superintendent who prioritizes continuous leadership development provides the essential leadership necessary to sustain leadership development initiatives. This study focuses on the effectiveness of leadership development within large school districts. The results of the study provided a view of the perceptions of principals, using focus group interviews and survey questionnaires. The researcher utilized individual interviews with superintendents to glean information about the challenges they encounter in developing principal leadership, as well as the specific structure, design, and implementation of leadership development programs. Leithwood's (1994) model of transformational school leadership (TSL) provided the conceptual framework for this study. This model's focus on the development of followers within a school context makes it an ideal method to determine the effectiveness of school-based leadership development. [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.]