Objective: To review the economic burden of Generalized Anxiety Disorder (GAD) by examining published North American studies and to use this information to define burden and cost of illness among patients with GAD. Methods: A systematic review of the literature was conducted using a PICO (Population, Intervention, Comparison, Outcomes) form to guide the search strategy. MEDLINE, EMBASE, and Cochrane Library databases, and selected websites, were examined. The search was limited to papers published in English between 1987 and 2007. Studies examining outcomes from mixed patient populations, combination therapies or non-pharmacological interventions were excluded. Results: The initial search yielded a total of 1999 articles, of which approximately 100 met predetermined inclusion criteria. The studies revealed 12-month prevalence rates ranging from 1.6–3.0%. GAD prevalence was higher among females compared with males and generally decreased with age. Comorbid mental disorders were common among patients with GAD, particularly depressive disorders, and were highly predictive of GAD onset and persistence. GAD was also associated with a substantive reduction in health-related quality of life. SF-36 scores in one study were 12–28 points lower among patients with GAD compared with the general US population (1). The health care resource utilization costs associated with GAD were considerable, although varying patterns of disease identification and treatment made the extent of this utilization difficult to quantify. Patients with GAD showed significantly higher medical care charges ($2375 vs. $1448, P=0.006) than patients without GAD (2). Conclusion: GAD, along with other anxiety disorders, exerts substantial cost-related burdens on society, driven in part by under-recognition and under-treatment of the disorder. Increased awareness, evidence-based treatment selection and appropriate early intervention could help to alleviate this burden.