Panic disorder (PD) has been linked to respiratory abnormalities ranging from benign chronic hyperventilation with associated hypocapnia to hypersensitive respiratory control systems. We will present data on respiratory variability measures of panic disorder patients vs. normal controls subjects. Respiratory measures were collected while subjects lay supine breathing room air, in a respiratory canopy system. We examine baseline respiratory measures to determine if 1) greater variability is specific to panic disorder, 2) if there is a relationship between greater variability and baseline anxiety, 3) if there is a relationship between the severity of patient’s illness, life stress events, and clinician rated scales with greater respiratory variability and 4) if anti-panic treatment alters respiratory variability.