Some years ago we edited a general casebook on behavior therapy that was well received. However, those professors who used the book as an adjunct text in child behavior therapy courses were concerned that only 9 of the 26 chapters dealt with the clinical application of behavioral prin ciples to children. Their contention was that a specific casebook on the topic was very much warranted. In considering their comments we took a closer look at the child behavior therapy area and were struck with how diverse it was, how it had expanded, and how it had matured over the last three decades. Given this apparent gap in the literature, we decided to devote an entire casebook to both the standard and the more innovative clinical applications to the behavioral problems presented by children. The resulting book, containing 28 chapters, is divided into two parts. In the first part, in a chapter entitled "How the Field Has Moved On," we briefly trace the historical roots of child behavior therapy, detail the relationship of psychiatric diagnosis and behavioral assessment, and con sider the importance of developmental norms, psychological testing, ef forts at prevention, and behavioral medicine. The bulk of this book, of course, appears in the 27 cases presented by our respective experts. Each of the treatment cases is presented in identical format for pur poses of clarity, consistency, and comparability."