In this era of accountability and significant school reform, efforts to improve schools increasingly look to the principal to spearhead change efforts at the school level. Good principals are the cornerstones of good schools. Without a principal's leadership efforts to raise student achievement, a school cannot achieve its fundamental academic mission. The principal is seen as a key agent at the school level, initiating change by raising the level of expectations for both teachers and students. One promising, but largely unexplored avenue to understanding principal motivation and behavior is principals' sense of efficacy. Self-efficacy is a perceived judgment of one's ability to effect change, which may be viewed as a foundational characteristic of an effective school leader. This paper reports on three studies that were conducted in the search for a reasonably valid and reliable measure to capture principals' sense of efficacy. (Contains 3 tables and 2 notes.)