Twenty-four panic disorder patients and 25 nonclinical subjects underwent double-breath inhalations of 5, 10, and 20% carbon dioxide (CO2) or room air. All subjects were blind to inhalation content and were required to guess if the inhalation contained CO2. There was no significant difference between groups in the accuracy with which they were able to detect CO2 at any concentration. Similarly, the number of somatic symptoms reported to each inhalation did not differ between groups. The findings question suggestions that individuals with panic disorder are more accurate at detecting changes in physiology than other individuals.