The authors trace the history of the classification of anxiety disorders, beginning with a detailed discussion of Freud's work on anxiety-neurosis as a basis for subsequent work. They discuss how anxiety disorders were described in DSM-I and DSM-II where Freud's concept of the anxiety neurosis was used as a major organizing principle. The revolutionary change in DSM-III is described in which the term and organizing principle of neurosis was dropped. The controversies that have arisen as a result of changes in DSM-III-R are discussed, particularly as they relate to compatibility with the International Classification of Diseases-10 (ICD-10) and especially with respect to the relationship and priority of panic and agoraphobia. Finally the authors discuss the process by which decisions will be made in DSM-IV where changes will be based on systematic reviews of empirical evidence whenever possible.