OBJECTIVE The goal of this study was to test the validity of generalized anxiety disorder as an independent diagnostic entity and to evaluate the prevalence and type of other psychiatric disorders coexisting with generalized anxiety disorder. Although a few published studies have addressed the subject, this study presents data from a larger group of subjects and excludes concurrent major depression as a potential confound. METHODS The authors studied patients with a primary diagnosis of generalized anxiety disorder assigned after evaluation with the Structured Clinical Interview for DSM-III-R. Patients with a concurrent major depressive episode were excluded. All diagnoses for which the patient met criteria were determined, including lifetime occurrence of major depressive episode and substance use. RESULTS One hundred nine patients with generalized anxiety disorder were included in the analysis. Twenty-eight (26%) of these patients were not given any other lifetime psychiatric diagnosis. The most prevalent comorbid diagnoses were social phobia (25 [23%] of the patients) and simple phobia (23 [21%] of the patients). Forty-six (42%) of the patients with generalized anxiety disorder had experienced at least one major depressive episode during their lifetime. CONCLUSIONS These results support previous findings of high rates of psychiatric comorbidity in generalized anxiety disorder and validate the usefulness of generalized anxiety disorder as a separate diagnostic entity.