The psychotherapy case formulation model is integrative, and takes an evidence-based approach to treatment by mental health practitioners. Formulating cases is an essential component of psychotherapy training and practice, yet beginning therapists often struggle to organize their ideas about the client and apply theory to the case. The model presented in this volume is designed to adapt to any theory of therapy, any treatment manual, and any component of a theory. The author emphasizes case formulation inferences that are based on theories with supporting evidence, expert knowledge about formulation, and steps to enhance sound reasoning in case formulation. This book incorporates a focus on culturally responsive therapy by presenting a cultural perspective, including consideration of race and ethnicity, sex and gender, socioeconomic status, and religion and spiritual orientation, on case formulation and providing guidance on incorporating culture into a case conceptualization. It draws heavily upon cognitive science research to support evidence-based practice in case formulation, and includes a case example and checklist to illustrate the principles and steps of formulation. Topics investigated include the slippery definitions of mental disorders, approaches to assessing behavior and selecting a treatment approach, and treatment planning. The book also explores the role psychiatric diagnosis plays in psychotherapy, its limitations, its societal impacts, and what it contributes uniquely to case formulation.