The question of how to optimally organize into chapters and label the different categories of mental disorders is an important one for DSM-5 and ICD-11. The grouping of mental disorders, or meta-structure, should arguably reflect knowledge on the validity of different conditions and their relationships, and should ideally contribute to improving the clinical utility of the nosology by guiding clinical assessment and management. The DSM-5 Anxiety, Obsessive-Compulsive Spectrum, Posttraumatic, and Dissociative Disorders Workgroup has reviewed the nature of anxiety disorders, the possibility of including a new category of obsessive-compulsive spectrum disorders in the DSM-5, and the concept of traumatic stress disorders. It is difficult to devise a perfect nosology that dissects nature at her joints; instead, any particular approach to the meta-structure would seem to have pros and cons that must be carefully weighed. Despite the imperfections of any meta-structure, we are hopeful that each revision of the nosology will bring with it greater diagnostic validity and clinical utility.