The goal of psychotherapy, simply put, is change - change for the better. In practical terms, that means figuring out which interventions, which kinds of therapy, work for different kinds of psychological problems or disorders. Which is the best choice? And more important, how can therapeutic change be measured? These questions have challenged practicing psychotherapists for decades. The research on patient change has been widely studied, but the sheer range of conclusions has been frustrating to therapists looking for practical information that they can use right away. This text takes a step toward resolving these frustrations. It brings together top experts in psychotherapy, and leading figures in clinical research, to put together what the author calls a core relational battery. This core battery is proposed as a reliable tool for measuring change in three basic diagnostic areas: mood, anxiety, and personality disorders. The discussion is organized around four key questions: What should a core battery look like? What needs to be measured? What criteria should be adopted in selecting measures? And what measures should be used?