All assessments and treatment sessions are at no cost to the patients. 50% of the patients will randomly be assigned to the D-Cycloserine (DCS) condition, and 50% of the patients will be assigned to a placebo condition. D-Cycloserine is FDA-approved for the treatment of Tuberculosis. However, recent research in other anxiety disorders has shown that D-Cycloserine plus Behavior Therapy is more effective than Behavior Therapy alone.