A comprehensive theory of panic must explain not only the cause(s) of episodes of panic but also why and when panic episodes terminate. Accordingly, we conducted a set of three studies on participants with panic disorder in order to investigate these aspects of panic episodes. In Study 1, we asked participants to monitor their panics prospectively, paying particular attention to the episodes' conclusions and the time period which followed. Results from Study 1 were consistent with earlier retrospective studies, showing that people engage in safety and other behaviors in an attempt to end their panics. We also collected information from the participants on beliefs about panic termination and the post-panic period. Study 2 was designed to determine if a post-panic refractory period occurs. Participants were asked to complete a hyperventilation exercise, and then to repeat the exercise a second time. Results from this study provide scant evidence of a post-panic refractory period. Study 3 was a more ecologically valid version of Study 2, in which participants were asked to re-trigger panics that occurred in their natural surroundings. Again, there was little support for a post-panic refractory period. Results are discussed in terms of cognitive-behavioral and biological theories of panic disorder.