Grounded in the updated PTSD Prevention and Treatment Guidelines of the International Society for Traumatic Stress Studies (ISTSS), the third edition of this definitive work has more than 90% new content, making it virtually a new book. Chapters describe PTSD assessment and intervention practices that have been shown to work and provide practical, real-world implementation guidance. Foremost authorities address the complexities of trauma treatment with adults, adolescents, and children in diverse clinical contexts. The book delves into common obstacles and ways to overcome them, when to stop trying a particular approach with a client, and what to do next. Special topics include transdiagnostic interventions for PTSD and co-occurring problems, dissemination challenges, and analyzing the cost-effectiveness of treatments.