Panic disorder runs a chronic or episodic course. In addition to panicking, patients remain clinically anxious and also chronically hyperventilate between attacks. Panic patients chronically hyperventilate in the attempt to keep pCO2 low, thereby preventing activation of the brain's asphyxiation alarm. However, panic patients in the non-panic state have EEG abnormalities, as well as abnormal cerebral blood flow and cerebral glucose metabolism. These abnormalities probably indicate cerebral hypoxia secondary to chronic hyperventilation. Chronic hyperventilation in panic patients may therefore engender a self-perpetuating mechanism. Prolonged cerebral hypoxia following chronic hyperventilation may contribute to the chronicity and severity of panic and anxiety symptoms, as is the case in sufferers of chronic obstructive pulmonary disease. Aerobic exercise may help panic patients to restore normal ventilatory patterns and mitigate adverse effects on the brain of chronic hyperventilation. As panic attacks are paroxysmal episodes of anxiety, knowledge gained from studies of panic disorder can be extrapolated to anxiety in general. Aerobic exercise may prove an adjunct treatment for anxiety that is non-pharmacological, non-addictive, and one that has few adverse effects and contraindications. As an extra bonus, it improves patients' self-esteem and reduces the risk of heart diasease and stroke.