For the purpose of clinical analysis of secundum atrial septal defect, the patients with atrial septal defect operated on during the period from Aug. 1959 to Aug. 1983 were analysed. The age of the patients was ranged from 3 months to 60 years and there were 132 males [45.3%] patients and 145 female patients [54.6%] in this series. The most frequent type was oval type defect in 219 [86.9%]. The PAPVC were present in 7 patients of high defect group. Clinical analysis revealed 53 patients [19.9%] were asymptomatic. The QP/QS above than 3.61 were 45 patients and less than 1.5 were 24 patients. The pulmonary artery pressure was 10 to 100 mmHg. The majority of the defects were closed in primary suture and closed with a Dacron patch in 19 patients. The postoperative complications occurred in 35 patients [13.1%] and the most frequent complication was wound problem which was present in 10 patients. The hospital mortality rate was 1.6%.[KTCS 1983;4:511-517]