The purpose of this special issue is to explain the advantages of using administrative data generated by states and school districts for research in special education, illustrate their use in special education policy studies, and encourage more such analyses. In this introduction to the special issue, we define and distinguish large administrative data sets, discuss types of special education policy questions that are appropriate for addressing with administrative data, provide a high-level overview of methods that are commonly used with such data, discuss examples of published analyses that use each method, note some of the limitations to using administrative data, and briefly introduce articles in the special issue.