Advances in measurement of child and adolescent social, emotional, and behavioral functioning and clinical disorders have been remarkable and remarkably reviewed in the prior articles. This commentary identifies common themes that emerge from the articles, discusses the proliferation of measures, and raises considerations regarding how one might proceed in developing evidence-based assessment (EBA). Developing EBA might begin by delineating the different purposes of assessment and then, for each purpose, identifying the special requirements and then the criteria for stating when these requirements are met. To illustrate the special requirements of different assessment goals, monitoring of patient progress in treatment is discussed.