ABSTRACT
The introduction to the Special Issue on Validity Studies lays out the rationale and provides an overview of the four articles comprising the issue. Each of the articles focuses on the validation of a specific instrument for a given purpose. The set represents a range of assessment types and uses, including the assessment of reading strategy use, an observation measure of special education teachers, a next generation alternative assessment for students with the most significant cognitive disabilities, and a student self report survey to assess and respond to individual risks and needs that may lead to truancy and/or school failure, Each article presents a unique case of using evidence to support the argument that scores from a given instrument provide both intended inferences and valid information for a given purpose. The concluding commentary summarizes lessons learned and challenges remaining for the field.