This article reports on differences between expert and aspiring principals. Following the work of Leithwood and colleagues, we asked expert and aspiring principals to respond to ill-structured written problem scenarios. Our sample of 44 included 20 expert principals and 24 aspiring principals. The aspiring principals were from a cohort of participants in a professional development program for aspiring principals in a large Midwestern urban school district. Drawing from that same school district, the expert principals were selected based on an analysis of longitudinal teacher survey data and student achievement data. We found statistically significant differences between expert and aspiring principals on five problem-solving processes, three of which were in line with prior hypotheses generating research on principal expertise. (Contains 2 tables and 4 notes.)