The present study was performed to evaluate hemodynamic effects on the pericardial patch graft for stenosis of right ventricle outflow tract in 19 patients of tetralogy of Fallot. The stenosis of right ventricle outflow tract was associated with or without pulmonary annular nar-rowing, pulmonary valvular stenosis, and hypoplastic narrowing of pulmonary artery. Total correction of tetralogy of Fallot was performed under cardiopulmonary bypass with moderate hypothermia and cardioplegic cardiac arrest. Ventricular septal defects were closed with Teflon patch graft. The chamber pressures in the heart were measured before and after a total correction of tetralogy of Fallot. The data of pressure measurement and the results of postoperative observation of pericardial patch were as followings: 1. Systolic and diastolic pressure of right ventricle was decreased after operation from 96.0±14.7/10.0±14.4 mmHg to 61.0±13.1/8.0±9.3mmHg. 2. Systolic and diastolic pressure of pulmonary artery was increased after operation from 18.0±5.6/ 10.0± 5.5 mmHg to 31.0± 10.7 / 14.0±4 .9mm Hg. 3. Preoperative pressure gradient between right ventricle and pulmonary artery was decreased immediately after operation from 78.0mmHg to 30.0mmHg. 4. It was observed that excellent widening effects of right ventricle outflow tract was resulted from pericardial patch graft. 5. No postoperative bleeding from pericardial patch graft was observed. 6. Aneurysm formation of pericardial patch was not be observed during 1 to 6 years postoperative periods.[KTCS 1982;1:61-66]