Social phobia is a common and often disabling condition, with an etiology that is not established. There is evidence at several levels for an interplay of biological and psychological processes in social phobia. Genetic studies show that both genetic and environmental factors are important, with evidence pointing to associations with 2 genetic conditions, autism and fragile X syndrome. Behavioral inhibition has emerged as an important precursor to social phobia and possibly to other anxiety disorders. Epidemiologic and clinical studies have suggested that factors within the family environment, such as overprotection, overcontrol, modeling of anxiety, criticism, and in some cases abuse, can play a role in the development of social phobia. During childhood, complex interactions between brain system disturbances that mediate responses to negative social cues and factors in the social setting may lead to the development of a distorted set of internal "blueprints" for social behavior. The impact of severe social anxiety on brain systems that mediate behavioral change may prevent patients from learning better "blueprints." These can be taught through cognitive-behavioral therapies. The effective control of social anxiety with medications enables patients to recover; whether recovery can last after discontinuation of medications may depend on whether a new "blueprint" has been developed and whether stable changes in affected brain systems have occurred. Neuroimaging techniques are at the early stage of identifying abnormalities at the neurotransmitter and systems levels.