We as a field believe that school principals can acquire new expertise by participating in principal preparation and professional development programs; however, we have few methodologies to measure leadership expertise, especially expertise that links leadership to improved student learning. In this article, we present the results of a study that examines two instruments for measuring leadership expertise, principal surveys and open-ended scenarios. First we make the case regarding the need for measurements of expertise. Next we discuss the conceptual definitions of expertise in general and present the specific domains of leadership expertise we attempt to measure. Finally, we present the results of a study that implemented two measures of leadership expertise: principal surveys and open-ended scenarios. The descriptive statistics, correlations, and examples we present in this article offer mixed results regarding the strengths and weaknesses of the various methods to conceptualize and measure leadership expertise. (Contains 1 figure and 6 tables.)