The clinical studies were performed on 757 patients who had been admitted to Severance Hospital from May, 1964 to June, 1975 with the diagnosis of congenital heart disease. The following results were obtained; 1. Among 757 patients, cardiac catheterization was performed on 367 patients. 2. Four hundred and thirty eight patients were male and 319 were female. Over half of them were below two years of age, but among 357 cardiac catheterized patients, 137 (37.3%) patients were ranged between 6 to 10 years. 3. V.S.D., Tetralogy of Fallot, P.D.A., A.S.D. were found in order of frequency. 4. Among 757 patients, combined extra-cardiac anomalies were found in 42 patients, and 14 patients were with Downanjx syndrome. 5. Among 367 cardiac catheterized patients, 164 (44.7%) patients had cardiac operations, and among these, 18 (11.0%) patients died including 7 patients of Tetralogy of Fallot.