In this paper, the authors describe a cost analysis framework and approach that can be easily understood by a range of relevant audiences and that has been successfully used to estimate the costs of a range of professional development initiatives. The paper illustrate its use by drawing on the authors' experience applying the framework in three different applications. In three separate studies, they used the cost framework to examine the following types of professional development initiatives: (1) Pathways to Teaching Careers program; (2) National Board Certification candidacy and support programs; and (3) Principal professional development initiatives. (Contains 9 endnotes.) [This paper was commissioned by The Wallace Foundation. For the main report, "Preparing School Leaders for a Changing World: Lessons from Exemplary Leadership Development Programs. School Leadership Study. Final Report," see ED533003.]