Book excerpt: Obsessive-compulsive disorder 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. However, 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 provides the reader with an understanding of 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, the authors provide tips on receiving and giving supervision to trouble-shoot commonly encountered problems, resulting in a guide that can help clinicians at all levels of experience.