Abstract The Diagnostic and Statistical Manual (DSM-III) contains little specific information pertaining to the ages of onset of anxiety disorders. Such information is of clinical and research value in understanding the natural history of mental illnesses, in determining which of several possible etiologies for a given diagnosis may be relevant for a particular patient, and in testing theories of psychopathology or pathophysiology. Age-of-onset data is presented for 423 psychiatric outpatients seen at a University Hospital—based anxiety disorders program. All adult anxiety disorders are represented except posttraumatic stress disorder. The relevance of this information is discussed in terms of past research on ages of onset of the anxiety disorders, and in its bearing on the psychiatric diagnosis of these conditions.