This study involves cognitive behavioral therapy (CBT) and a medication called D-cycloserine (DCS), which is thought to help reduce panic symptoms more effectively by interacting with N-methyl-D-aspartate (NMDA) glutamate receptors, facilitating many forms of learning including the extinction of fear. Participants will be randomly assigned (like flipping a coin) to receive either DCS or a placebo in addition to CBT.

This study consists of cognitive behavioral therapy (CBT) including exposure to physical sensations and feared situations, which have been demonstrated to be effective for many individuals with panic disorder.

All assessments and treatment sessions are free of charge. Half of the patients will be randomly assigned to receive D-cycloserine (DCS) and half wll be assigned to receive a placebo. Although DCS is used in humans to treat tuberculosis, it has not been FDA approved for this indication. Recent research in other anxiety disorders has shown that DCS plus behavior therapy is more effective than behavior therapy alone.

This treatment study had two active interventions. All patients will receive CBT and the researchers expect that everybody will improve from this treatment. However, it may be that those patients in the DCS intervention will improve somewhat more than those in the placebo intervention.

The treatment will be structured with at home practice and repeated assessments. Assessments are extremely important as they guide the treatment and provide the study investigators necessary information about the treatment. The treatment consists of 5 sessions (once a week) plus a one week post-treatment assessment and follow-up assessments at one month and six months.

Inclusion Criteria:

• Principal diagnosis of panic disorder

Exclusion Criteria:

• History of psychotic disorders or bipolar disorder
• Substance dependence
• Pregnant or breastfeeding
• History of a medical condition that may increase the risks of taking the study drug