Cardiopulmonary adaptation during exercise was compared in patients with an extracardiac total cavopulmonary connection and controls with biventricular repair of Fallot's tetralogy. Heart rate, blood pressure, respiratory frequency, and transcutaneous oxygen saturation increased with treadmill exercise intensity below grade 3 in patients who had undergone extracardiac total cavopulmonary connection. When exercise intensity exceeded grade 4, blood pressure and oxygen saturation decreased continuously, respiratory rate kept increasing, and heart rate showed no significant change. In cases of fenestrated cavopulmonary connection, heart rate peaked at grade 5 exercise intensity, and blood pressure at grade 4; but both peaked at grade 3 in non-fenestrated patients. During all exercise testing, fenestrated patients had a higher respiratory rate but lower oxygen saturation than those without fenestration. Exercise tolerance was below normal after a cavopulmonary connection, but patients still adapted to exercise below grade 3 with appropriate increases in heart rate and respiratory rate. Due to insufficient right heart systems, patients with a cavopulmonary connection showed obvious exercise limitation at exercise intensity grade 3 or more. Total exclusion of the right heart system may also have adverse effects on the sinoatrial node, leading to impaired heart rate regulation.