The underdevelopment of the right ventricular outflow tract is the essence among the main components of the tetralogy of Fallot. The detail and exact imformations about the states of the outflow tract in each patient with tetralogy of Fallot are very important to cardiac surgery. Forteen patients of tetralogy of Fallot (12 undergone open heart surgery and 2, palliative) are available for their clinical chart and for cardiac angiography reviews. Analysis of them focusing the right ventricular outflow tract discloses the following results: 1. Average ratios of the systole to diastole of the pulmonary infundibulum are 0.63$pm$0.03 with the range of 0.44 to 1.0 on P-A, and 0.64$pm$0.12 with the range of 0.5 to 0.83 on lateral projections. These results indicate relatively fixed infundibular stenosis of TOF. 2. Average infundibular systole to pulmonary bulb ratios are 0.24$pm$0.05 on P-A, and 0.36$pm$0.17 on lateral projections, which mean the underdeveloped and narrowed infundibulum more han the pulmonary trunk in TOF. 3. Average pulmonary to aortic bulb ratios are 0.59$pm$0.01 on P-A, 0.54$pm$0.01 on lateral projections. These suggest hypoplasia of the pulmonary trunk and anteriorly displaced conus septum and truncus septum from a developmental point of view. 4. The overriding degree of the aorta in our series are from 25% to 50% by Kjellberg et al classification.