Endocardial cushion defect is a rare congenital heart disease. From September 1985, we experienced 20 cases of endocardial cushion defects and postoperative follow up was taken.We reviewed preoperative clinical data, echocardiography, cardiac cath data, operative method & time. After operation, we performed echocardiography and examined mitral valve function & integrity of patch closure sites. Postoperative follow up was taken regularly & follow up period was from 2 month to 91 months. Several postoperative complications were overcome with adequate treatment. There were 3 cases of early death and mortality rate was 15% [3/20].