Anxiety disorders are the most common of all psychiatric illnesses and result in considerable functional impairment and distress. Recent research developments have had a broad impact on our understanding of the underlying mechanisms of illness and treatment response. Working with patients who have an anxiety disorder can be highly gratifying for the informed psychiatrist, because these patients, who are in considerable distress, often respond to proper treatment and return to a high level of functioning. The major anxiety disorders presented in this chapter are panic disorder, generalized anxiety disorder (GAD), social anxiety disorder, specific phobias, obsessive-compulsive disorder (OCD), and posttraumatic stress disorder (PTSD). Table 12–1 presents a summary overview of the prevalence, gender ratio, and comorbidities of the major anxiety disorders.