OBJECTIVE: Regular physical activity is anxiolytic for both healthy subjects and patients with panic disorder. However, the acute antipanic activity of exercise has not yet been studied systematically. METHOD: The effects of quiet rest or aerobic treadmill exercise (30 minutes at 70% of maximum oxygen consumption) on cholecystokinin tetrapeptide (CCK-4)-induced panic attacks were studied in a crossover design in 15 healthy subjects. The effects were measured with the Acute Panic Inventory. RESULTS: Panic attacks occurred in 12 subjects after rest but in only six subjects after exercise. In both conditions, CCK-4 administration was followed by a significant increase in Acute Panic Inventory scores; however, prior exercise resulted in significantly lower scores than quiet rest. CONCLUSIONS: Aerobic exercise has an acute antipanic activity in healthy subjects. If the authors’ results are confirmed in patients, the optimum intensity and duration of acute exercise for achieving antipanic effects will have to be characterized.