Social anxiety disorder, also known as social phobia, is a common and disabling psychiatric illness that is characterized by an excessive fear and/or avoidance of situations in which an individual feels scrutinized by others and is fearful of a negative evaluation by others. Although it is the most common of the DSM-IV anxiety disorders, there is a dearth of clinical neurobiological research on social anxiety disorder and few preclinical models. This review focuses on the generalized subtype, which involves the fear of a wide range of social situations, with the goal of proposing several neurobiological mechanisms that may account for the symptoms of this disorder. We begin with an overview of three nonhuman primate models that are particularly relevant to social anxiety. Next, we review recent literature in the clinical neurobiology of social anxiety disorder, focusing on important findings in developmental neurobiology and genetics. Our findings suggest that social anxiety disorder should be reconceptualized as a chronic neurodevelopmental illness instead of an episodic de novo adult disorder, a semantic distinction with important treatment implications.