One thousand cases of open heart surgery had been performed in the department of thoracic and cardiovascular surgery of Sejong General Hospital From January 1983 to July 1986. And also, 152 cases of non open heart cardiac surgery and 16 cases of balloon valvuloplasty had been performed during same period. Among the 1000 open heart cases, 824 were congenital cardiac diseases and 176 were acquired heart diseases. In congenital heart patients, 585 were acyanotic and 239 were cyanotic. Acyanotic group were consisted of 406 VSD, 107 ASD, 23 PDA, 19 ECK, 16 PS, 7 AS and 7 other rare cardiac cases. And cyanotic group were composed of 178 TOF, 18 trilogy, 11 DORV, 8 TGA, 7 pulmonary atresia, 5 Ebstein's anomaly, 5 univentricular heart and 7 other rare cardiac diseases. Majority of the acquired heart cases were valvular heart diseases. And there were also 4 cardiac tumors, one endomyocardial fibrosis, and one ascending aortic aneurysm in acquired heart disease group. In valvular patients, 158 had valve replacement surgery and 12 had valve repair surgery. The operative results were as follow : Overall operative mortality, 7.5% : acyanotic, 3.4% : cyanotic, 16.7% and aquired heart disease, 8.5%.