The report is concerned to our experience of 12 cases of open heart surgery under the extracorporeal circulation at the Department of Thoracic and Cardiovascular Surgery, Chosun University Hospital during the period between Nov, 1979 and April, 1983. 1. There were 4 cases of congenital anomaly and 8 cases of acquired heart disease. 2. There were 6 male and 6 female patients with a mean age of 20 years. [range 9 to 33 years]. 3. The cases induced 2 ventricular septal defect, 2 atrial septal defects and 8 acquired valvular heart diseases. 4. The surgical managements were 2 primary repair for atrial septal defect and 2 patch closure for ventricular septal defect, 1 triple valve replacement [AVR MVR TVR], 1 aortic valve replacement, 4 double valve replacement [AVR MVR] and 2 open mitral commissurotomy for pure mitral stenosis. 5. The average cardiopulmonary bypass time was 61.5 minutes for congenital heart disease and 201.4 minutes for acquired valvular heart disease and the average aortic cross clamping time was 36.75 minutes for the former and 165.6 minutes for the latter. 6. Postoperatively, there were 1 Alopecia, 1 Electric burn and 1 wound infection as complication. 7. Overall operative mortality was 8.3%. 7. All patients received valve replacement were recommended anticoagulation with persantin [KTCS 1983;3:289-294]