Treatment of and research on anxiety disorders depends on the adequate conceptualization and measurement of these conditions. We review the history of the nosology of anxiety disorders and note that divisions of "neurosis" have inadvertently taken attention away from what is shared among conditions now classified separately. We note the changes in the definition of agoraphobia over time and the striking differences between DSM-IV and ICD-10 definitions. We mention ongoing controversies in the diagnoses of posttraumatic stress disorder, acute stress disorder, and generalized anxiety disorder. Finally, we discuss controversies surrounding the proper placement of obsessive-compulsive disorder and putatively related conditions in future diagnostic classifications. We hope that reviewing controversial aspects of diagnosis is useful to clinicians and researchers interested in the neurobiology of anxiety disorders.