Although university-based school administrator preparation programs are required by accreditation agencies to assess the dispositions of candidates, valid and reliable methods for doing so remain scarce. "The School Leaders Disposition Inventory"[C] (SDLI) is proposed as an instrument that has promise for identifying leadership dispositions grounded in transformational leadership theory. In this research report, the authors explain the development of the SDLI and report on a pilot study. With the instrument's internal consistency established, the SDLI will assist school leader preparation program personnel in assessing the degree to which candidates for school administrator positions reflect dispositions aligned with transformational leadership theory. (Contains 1 table.)