The use of an assessment center in identifying specific staff development needs of aspiring and practicing school principals was studied. The relationship between assessment center performance and subsequent staff development activities was studied by participant level (elementary, middle and junior high, and high school) and by participant experience (aspiring and practicing). Areas of exceptional performance and areas of needed improvement were also determined for 12 dimensions of administrative leadership by assessment center participants. The sample included 109 participants in the Center for Assessment of Administrative Performance at the University of Washington (Seattle). Data were derived from written records of participants and from surveys completed by 94 of the participants. A limited relationship between assessment center results and subsequent staff development activities was found for all participants, by level, type of school, and experience. The percentage of participants who received excellent ratings on all dimensions of administrative leadership was low. The following areas of need are identified: (1) resourcefulness; (2) decisiveness; (3) creativity; and (4) judgment. Recommendations are made to improve assessment centers and make them a useful method of sharpening the professional skills of principals and those aspiring to be principals. Four tables present study data. (SLD)