Clinical analysis was performed of 89 secundum type atrial septal defect patients operated on during the period from July, 15th, 1981 to March, 1987 in the Thoracic and Cardiovascular Surgery Department of Pusan National University Hospital. Secundum type ASD was 2`I.0% among all of congenital heart diseases operated in the same period. The age distribution of patients ranged from 3 to 41 years and sex ratio, male to female was 1.23 to 1.0. Common symptoms were exertional dyspnea 64.0%, frequent upper respiratory infection 43.8%, cyanosis 10.1% and fatigue 7.9%. The mean value of cardiac catheterization data of the group of ASD combined with another cardiovascular anomalies was compared with that of only ASD group. The amount of shunt showed not statistically significant difference between two groups [P>0.05] but pulmonary arterial pressure and pulmonary vascular resistance of combined group was significantly higher than that of only ASD group [P<0.02, P<0.01]. The difference of mean hemodynamic data between the age group below 20 years and above 21 years was not statistically significant [P>0.05]. All cases were operated under cardiopulmonary bypass. Among these 51 were closed directly and 38 were applied Dacron patch. Two most common associated cardiac anomalies were pulmonary stenosis [8 cases, 9.0%] and VSD [8 cases, 9.0%]. The most frequent postoperative complication was wound infection, One patient died of low cardiac output on 10th postoperative day and the overall operative mortality was 1.1%