Social justice and good governance both demand determination of whether tax expenditures-preferential provisions such as special exemptions, deductions, credits, or deferrals-are yielding the benefits anticipated in the original legislation, and if they are as good or better than policy alternatives in direct expenditure programs. The six case studies in this issue examine a variety of tax expenditures, some affecting human services programs such as housing and some aimed at broader investment purposes. Applying a range of evaluative, research, and analytic techniques, the authors demonstrate how publicly available data and the familiar tools of evaluation can be successfully used to examine the effectiveness, results, and impacts of tax expenditures. This is the 79th issue of the quarterly journal New Directions for Evaluation.