Probably no effort has been more successful than the Interstate School Leaders Licensure Consortium (ISLLC) in capturing the current complexity of the principal's role and in providing direction for the professional development and selection of principals. As more states require universities to restructure training programs to align with the ISLLC standards, and as more principal assessment and performance evaluation systems are based on them, it is important to continually assess the relationship of the standards to the performance of effective administrators. This article describes a study that examined the extent to which Washington State superintendents perceived principals identified as "successful" as demonstrating mastery of the six ISLLC standards. Additionally, superintendents were asked to rank each of the six standards in order of importance to a principal's effectiveness. Findings of this study, when compared with the findings of McCown, Arnold, Miles, and Hargadine (2000), Coutts (1997), and Cox (2003), suggest that while all six ISLLC standards are essential to a principal's success, practitioners do not view all of them to be of equal importance. Implications for principal preparation programs related to the concentration of training time and the allocation of resources across standards also are discussed. (Contains 1 figure and 2 tables.)