Cardiac catheterization and submaximal exercise testing was performed in 38 patients after repair of tetralogy of Fallot (TF), and compared to 6 control patients who had functional murmurs. Cardiac index, heart rate, and stroke volume index were significantly lower in the TF group than in the control group. Right and left ventricular end-diastolic pressure increased significantly during exercise, which was not found in the control group. Total pulmonary vascular resistance (TPVR), which decreased significantly with exercise in the control group, did not change remarkably during exercise. TPVR was significantly higher in the TF group than in the control group both at rest and during exercise. Several factors were compared between patients with good cardiac index (> 5.0 l/min/m2; Group 1) and poor cardiac index (< 5.0 l/min/m2; Group 2) during exercise. Stroke volume index, right ventricular ejection fraction at rest were significantly higher in Group 1 than Group 2. TPVR, right and left ventricular end-diastolic and end-systolic volume index were significantly lower in Group 1 than in Group 2. There was no significant difference in heart rate, left ventricular ejection fraction, residual pulmonary stenosis, right to left ventricular systolic pressure ratio, and severity of pulmonary regurgitation between two groups. These findings indicate that abnormalities of exercise tolerance in patients after repair of TF were related to poor response of heart rate, pulmonary vascular resistance, and systolic and diastolic ventricular function.