Five hundred cases of open heart surgery were operated in the Dept. of Thoracic and Cardiovascular Surgery, Pusan National University Hospital from July, 1981 to October, 1986. The clinical data were summarized as follows: 1. The age distribution of congenital heart disease patients was 2 to 41 years old and mean age was 13.4 years and of acquired heart disease was 11 to 57 years old and mean age was 32.7 years. 2. There were 319 cases [63.8%] of acyanotic congenital heart anomalies, 56 cases [11.2%] of cyanotic anomalies and 125 cases [25.[%] of acquired heart disease. 3. For myocardial protection, Bretschneider and potassium glucose solution had been used as cardioplegic solution and since 1983, GIK solution is being used repeatedly every 30 to 40 minutes time interval with excellent results. 4. The ingredient of the priming solution is Hartmann`s solution, mannitol, sodium bicarbonate, potassium, chloride, fresh ACD whole blood, calcium chloride, heparin and dexamethasone. 5. There were 94 cases of mild hypothermia, 280 cases of moderate hypothermia and 126 cases of intermediate hypothermia. 6. The overall mortality was 8.2%. And the mortality rate in each disease entity is 2.5% in acyanotic congenital cases, 33.9% in cyanotic congenital cases and 11.2% in acquired heart disease.