Panic disorder with or without agoraphobia is a common anxiety disorder, occurring in 3.5 % of the population (Kessler, et al., 1994). Although the study of panic disorder has advanced in recent years, with the availability of a growing number of treatments with reported efficacy in clinical trials and practice, acute and longitudinal follow-up studies of patients with panic disorder suggest that many individuals remain symptomatic despite treatment (Pollack and Otto, 1994). However, there is no systematic data currently available to guide the treatment of patients with panic disorder who remain symptomatic after initial intervention.