The Woodcock?Johnson III (WJ III) is an extensive revision of its predecessor, expanded in depth, breadth, and complexity. It is widely used for assessing the cognitive abilities, oral language capabilities, and academic achievement levels of children, adolescents, and adults. The WJ III includes extensive examiner and technical manuals, and several interpretive texts are available. Although much is already written about how to interpret the WJ III, a need exists for documenting its clinical utility, particularly from a scientist?practitioner perspective. To address this need, WJ III Clinical Use and Interpretation presents a wide variety of exemplary clinical applications of the WJ III from its leading experts. In the introductory chapter of this volume (Chapter 1), Floyd, Shaver, and McGrew summarize the scientific evidence that can be used as a basis for interpretation of the WJ III, particularly as it applies to the Tests of Cognitive Abilities (WJ III COG). The authors provide data that support interpretation of the WJ III Cattell-Horn-Carroll factor clusters. The evidence suggests that the WJ III can provide insight into cognitive ability deficits associated with a number of clinical conditions. Next, Read and Schrank (Chapter 2) articulate an analytic method for deriving qualitative information from observable attributes of an individual?s performance on the WJ III. Mather and Wendling (Chapter 3) explain how patterns of WJ III cluster and test scores can be used to inform instruction when gathered as part of an intensive diagnostic study of an individual. Although the focus of their chapter is on the WJ III Tests of Achievement (WJ III ACH), they describe how patterns of both the WJ III COG and WJ III ACH cluster and test scores can assist with interpretation and formulation of diagnostic hypotheses.