Ten patients suffering from panic attacks were studied in an effort to test the feasibility of measuring panic attacks via 24-h ambulatory heart rate monitoring. Subjects were also asked to record their activity level, anxiety level, and level of panic at 15-min intervals. Seven of the 10 patients reported panic attacks during the 24-h recording period; one patient reported two panic attacks. Three of the eight panic episodes demonstrated significant heart rate increases relative to activity level. Results suggest that ambulatory monitoring of panic attacks may be most useful with patients who suffer from more frequent and severe panic attacks and who have high heart rates (greater than 110) during these attacks.