Thirty-seven patients had undergone repair of a endocardial cushion defect between 1977 and Aug. 1983 in Seoul National University Hospital. Twenty eight had a partial defect, one intermediate defect and eight complete endocardial cushion defect. Tricuspid cleft was found in 4 cases and mitral cleft was in all p-ECD. Seven patients were of type C anatomy in c-ECD. Four patients had associated major anomalies, including three TOF in c-ECD, one coarctation in p- ECD. In p-ECD patients, the septal defect was closed with patch in all cases and the atrioventricular valvular insufficiency was corrected with MVR in 4 cases, TVR in 1 case and simple interrupted sutures in remainders. In c-ECD patients the septal defect was closed with single patch except one case. The atrioventricular valve was repaired with simple interrupted sutures except one MVR and TVR case. The operative mortality was 14.2% in p-ECD, 44.4% in c-ECD, but recent 3 years [1980-1983] mortality was 8.7% in p-ECD, 20% in c-ECD. More than grade III systolic regurgitant murmur was oted postoperatively in 4 cases of c-ECD and 3 cases of p-ECD. The operative risk factors were preoperative NYHA classification, cyanosis, Rp/Rs, systolic pressure of main pulmonary artery and the degree of regurgitation of atrioventricular valves. The causes of death were low cardiac output syndromes, pulmonary complications and arrhythmias.