This chapter presents an overview of the descriptive epidemiology of anxiety disorders based on recently completed surveys of the general population. The overall prevalence of anxiety disorders is shown to be quite high, but with considerable variation from the most prevalent (specific phobias) to the least prevalent (agoraphobia without a history of panic disorder) disorders. Age-of-onset (AOO) of anxiety disorders is typically in childhood or adolescence and the course is often chronic-recurrent. Anxiety disorders are highly comorbid with each other and with other mental disorders. Because of their early AOO, they are often the temporally primary disorders in comorbid profiles, raising the question whether early interventions to treat anxiety disorders might have a positive effect on the onset, persistence, or severity of secondary disorders such as mood and substance use disorders. This possibility has not yet been extensively explored but warrants further study given the high societal costs of anxiety disorders.