This chapter follows the evolution of the nosology of the anxiety disorders through various editions of the APA's Diagnostic and Statistical Manuals (DSM) and culminates with a summary of some of the possible changes that might occur in the classification of anxiety disorders in DSM-5. Present-day anxiety disorders were also covered in some of the other DSM-I groupings. Given increased attention to disorders specifically related to children and adolescents, a new grouping, behavior disorders of childhood and adolescence, was added in DSM-II. The DSM-III diagnostic criteria for panic disorder were based on the Feighner criteria for anxiety neurosis. DSM-III-R field trials were conducted for agoraphobia without history of panic disorder (AWOPD) and generalized anxiety disorder (GAD). One new anxiety disorder was added to DSM-IV, acute stress disorder. The grouping of related disorders into spectra is a novel organizational approach proposed for DSM-5.