Social phobia, also known as social anxiety disorder, is a common, often debilitating condition. People with social phobia experience high levels of anxiety when they participate in social situations or perform in front of others. Approximately 80% of social phobia cases occur before the age of 18, and often precede other anxiety, mood, and substance abuse or dependence disorders. Physical symptoms typically accompany the intense anxiety caused by the disorder, and may include blushing, profuse sweating, trembling, nausea, and difficulty talking. Cognitive-behavioral therapy (CBT) has been shown to be an effective treatment method for most people with social phobia. Approximately 30% of people with the disorder, however, do not respond to CBT treatment. A better understanding of the neural mechanisms underlying social phobia and CBT's effect on these mechanisms will help physicians to better predict the best treatment for different patients. This study will evaluate the effect of CBT on how the brain processes emotional and behavioral responses to social stimuli in people with social phobia.