The main advances in our understanding of the status and nature of generalized anxiety disorder derive from analyses of the relationship between this disorder and its comorbid disorders, particularly major depressive disorder. A number of reports based on epidemiological and clinical samples suggest that the significance of comorbidity may not be greater for generalized anxiety disorder than for other anxiety and mood disorders. Although the issue of diagnostic specificity has not been resolved, the presence or absence of another disorder does not appear to alter the course of generalized anxiety disorder, the probability that it will impair the patient's functioning, or the pattern of onset. Recent progress in relation to treatment includes the development of psychological therapies that specifically target key characteristics of the disorder, such as worry. There is now reliable evidence to support antidepressant therapy as the first-choice pharmacotherapy, and initial reports of outcomes with longer term maintenance pharmacotherapy with antidepressants are promising.