Obsessive-compulsive disorder (OCD) can be a very disabling and distressing problem. Cognitive behavioural therapy (CBT) has been shown to be very effective in helping people to overcome OCD. OCD is a highly heterogeneous disorder, often complicated by contextual factors, and therapists are often left wondering how to apply their knowledge of treatment to the particular problems as they face them in clinical practice. This book guides the reader through understanding the background to and principles of using CBT for OCD in a clear practical ‘how to’ style. It also elucidates the particular challenges and solutions in applying CBT for OCD using illustrative case material and guidance on formulation-driven intervention. The book also addresses commonly occurring complexities in the treatment of OCD; for example, working with comorbidity, perfectionism, shame, and family involvement in symptoms. Throughout the book, tips are provided on receiving and giving supervision to troubleshoot commonly encountered problems. This book provides a guide to improved practice for clinicians at all levels of experience.