We will examine the degree to which DCS treatment can augment the clinical response in social phobia to CBT-exposure-based therapy. Specifically, we will study two groups of individuals with social phobia, both of whom will receive CBT. One group will receive placebo; a second group will receive 50 mg of D-cycloserine 1-2 hours before each exposure therapy session. We hypothesize that compared to placebo, DCS will produce greater reductions in social anxiety symptoms following CBT treatment. Finally, given that chronic social anxiety disorder virtually always begins during childhood, it is particularly vital to develop early interventions for the disorder. Accordingly, our trial will examine both adolescents and adults with the disorder.