From 1959 to Jun. 30 84, 1144 cases of various cardiovascular diseases were operated consisting of 421 open heart surgery under extra-corporeal circulation or hypothermia and 723 conventional surgery at department of Thoracic and Cardiovascular Surgery in National Medical Center. There were 470 congenital anomaly and 674 acquired lesions. Out of 470 congenital anomaly, acyanotic anomaly was 289 and cyanotic anomaly was 181. Among 647 acquired lesions, 473 was cardiac lesion, 87 was pericardial lesion and 105 was vascular diseases. Over all operative mortality was 9.0%, consisting of 7.6% for acyanotic, 19.3% for cyanotic anomaly and 6.8% for acquired lesion. Mortality for 723 conventional surgery was 6.2%, and 421 open heart surgery was 13.8%.