Sixty-eight consecutive patients have been subjected to total corrective surgery of tetralogy of Fallot at the Hanyang University Hospital between August 1975 and December 1984. Of these, the pressure of chambers and great arteries were measured, before and immediately following an operation in 39 of the survived group and 11 of the expired group. The values of postoperative peak pressure were correlated with the outcome of the operation. The result are as followings; 1] Compared to the average peak pressure of right atrium in the survived group, 14.46*4.16 mmHg, that in the expired group, 19.36*8.19 mmHg, was significantly lower, 2] Compared to the average systolic pressure of right ventricle in the survived group, 56.72z16.37 mmHg, that in the expired group, 70.45*15.26 mmHg, was significantly lower. 3] Compared to the average systolic pressure of pulmonary artery in the survived group, 33.26*12.95 mmHg, that in the expired group, 37.55*11.63 mmHg, was higher. But the difference was not significant. 4] Compared to the average peak pressure of left atrium in the survived group, 17.41*6.90 mmHg, that in the expired group, 31.18*12.47 mmHg, was significantly higher. 5] Compared to the average systolic pressure of left ventricle in the survived group, 103.82~12.83 mmHg, that in the expired group, 90.55*20.02 mmHg, was significantly lower. 6] Compared to the average value of the right ventricle-pulmonary artery systolic pressure gradient [RV-PA] in the survived group, 24.95a15.44 mmHg, that in the expired group, 35.09*17.01 mmHg, was significantly higher. 7] Compared to the average value of the right ventricle to left ventricle systolic pressure ratio [RV/LV] in the survived group, 0.55*0.15, that in the expired group, 0.80a0.20, was significantly higher. 8] Compared to the average value of the pulmonary artery-left atrium peak pressure gradient [PA-LA] in 15.85x12.29 mmHg that in the expired group, 4.18x6.00 mmHg, was significantly lower. It is, therefore, suggested that in the operating room, PA-LA is as valuable as RV - PA, RV/LV in making important surgical decision and predicting the prognosis.