Book excerpt: It is well documented that school leadership is second only to classroom instruction as an influence on student learning and achievement (Leithwood & Reihl, 2003; Wahlstrom et al., 2010, Ediger, 2014; Waters et al., 2003). Because principals directly impact schools’ academic capacity, effective principals are essential for the transformation of failing schools (Harvey & Holland, 2011). Assistant principal positions are a major stepping-stone towards principal positions; however, an assistant principal position does not provide appropriate training for a principal position (Fields, 2002; Koru, 1993; Kwan, 2009; Mertz, 2006; Webb & Vulliamy, 1995). It is important to know how principals and assistant principals perceive the knowledge, skills, and attributes (KSAs) needed to be an effective leader because leaders develop their leadership style and base their actions on their beliefs and perceptions. This study examines whether there is a significant difference in the perceptions of principals and assistant principals regarding the KSAs needed to be successful in their roles. The study further examines whether there is a significant difference in principals’ and assistant principals’ perceptions regarding KSAs based on gender, years of experience, ethnicity, and campus academic rating. This study used archival data collected from two larger studies entitled, “A Survey to Examine the Work, Attitudes and Perceptions of Public School Principals” (MacNeil, 2004) and “A Survey to Examine the Work, Attitudes and Perceptions of Public School Assistant Principals” (MacNeil, 2006). 305 principals and 371 assistant principals in a large metropolitan area of the Gulf Coast area of Texas participated in the study. The participants rated knowledge (of people, curriculum, law, and fiscal management), skills (interpersonal, communication, leadership, management, technical), and attributes (positive disposition, visionary, ethics and values, good communicator, organization) on a Likert scale. One-way and two-way MANOVA were used to answer research questions. The study revealed that principals and assistant principals perceive knowledge, skills and attributes needed to be successful in their roles differently. The most differences are in knowledge of law, leadership skills, and being visionary. The differences are also irrespective of gender, years of experience, ethnicity or campus academic rating. This information can be used in principal preparation programs as well as in principal and assistant principal professional development programs in school districts. The study also provides recommendations about the role of assistant principals who are in a promotion track.