Social anxiety disorder, or social phobia, is one of the most common mental disorders, yet it remains underrecognized and undertreated. Individuals with social anxiety disorder frequently have psychiatric comorbidity, including mood, anxiety, and substance abuse disorders, that can further impair a person's ability to function. This article reviews the literature on social anxiety disorder and explores questions regarding its prevalence, rates of recognition and treatment, and natural history. The association between social anxiety disorder and psychiatric comorbidity and suicide is reviewed, as well as quality-of-life issues, including the impact of social anxiety disorder on educational attainment, occupational functioning and financial dependency, marital status, and health care utilization. There is a need for further study and greater awareness among primary health care providers about the prevalence and treatment of social anxiety disorder.