Despite the established therapeutic value of interoceptive exposure, little is known about how to optimally deliver this procedure. In the most clinically tested panic disorder treatment package, individuals engage in three, minute-long trials of interoceptive exposure exercises such as hyperventilation, with each trial followed by the use of diaphragmatic breathing and a rest period until all anxiety-related body sensations have subsided. However, there are theoretical reasons to question the effectiveness of this method. For example, encouraging individuals to use controlled breathing to "manage" their sensations appears incompatible with the notion that anxiety-related body sensations are harmless. Similarly, the instruction to wait until one's body sensations have subsided to begin the next interoceptive exposure trial suggests that intense body sensations are to be avoided. For these reasons, many practitioners conduct interoceptive exposure in a more intensive manner in which individuals experience feared body sensations in a prolonged fashion, without attempting to suppress or avoid them, until they learn that the sensations are harmless. Despite the theoretical appeal of this latter approach, no studies have examined the effects of delivering interoceptive exposure in this manner. Indeed, very little is known about the effects of different methods of delivering interoceptive exposure on fear of arousal-related body sensations. Accordingly, the present study aims to test the effectiveness of different methods of delivering interoceptive exposure with the goal of generating recommendations for the optimal treatment of panic disorder and other clinical problems associated with the fear of anxiety-related body sensations.