Principles of Change constitutes a new approach to evidence-based practice in psychotherapy that goes beyond the traditional and unidirectional dissemination of research, whereby clinicians are typically viewed as passive recipients of scientific findings. Based on an extensive review of literature, it first offers a list of 38 empirically based principles of change grouped in five categories: client prognostic, treatment/provider moderating, client process, therapeutic relationship, and therapist interventions. Six therapists from diverse theoretical orientations then describe, in rich and insightful detail, how they implement each of these principles. The book also offers exchanges between researchers and clinicians on several key issues, including: how similarly and differently change principles are addressed or used across a variety of treatments; and how clinicians’ observations and reflections can guide future research. By presenting together these unique yet complementary experiences, Principles of Change will support synergetic advances in understanding and improving psychotherapy, laying the foundation for further collaborations and partnerships between stakeholders in mental health services.