OBJECTIVE: The authors determined the frequency of anxiety disorders in a large group of depressed outpatients seeking treatment. METHOD: The Structured Clinical Interview for DSM-IV was administered to 373 depressed outpatients. RESULTS: More than one-half of the patients met the full criteria for a current anxiety disorder, and more than one-half of the patients with an anxiety disorder had more than one. When partial remissions and anxiety disorder diagnoses classified as "not otherwise specified" were included, two-thirds of the patients had a current anxiety disorder and three-quarters had a lifetime history of an anxiety disorder. CONCLUSIONS: The majority of patients with a principal diagnosis of unipolar major depressive disorder have a comorbid anxiety disorder. Because antidepressant medications have differential efficacies for anxiety disorders, knowledge of the presence of a comorbid anxiety disorder in a depressed patient may have treatment implications.