Between 1989 and 1992, atrial septal defect secundum (ASD) were closed in 8 patients aged 51 to 77 years with the use of cardiopulmonary bypass. The notable characteristics in our cases were; 1) All but one had slight or moderate left to right shunt ratios. Although pulmonary hypertension was present, the obstructive pulmonary vascular change had not progressed so far. 2) Atrial fibrillation was present in 6 patients (75%) and some other cardiac lesions (atrioventricular insufficiency, ischemic heart disease, intracardiac anomaly) coexisted with ASD in a high frequency. And surgical procedures other than ASD closure were required in 5 patients. 3) We must take care to prevent cardiac complications (i.e., arrhythmia) as well as extracardiac malfunctions in postoperative care, because aged patients had some organic dysfunctions of respiratory, renal and hepatic systems. 4) Post-operative courses were satisfactory and there was no operative mortality. All patients obtained improvements in their quality of life. Consequently, we concluded that surgical closure is recommended even for aged patients with ASD, except for Eisenmenger's syndrome.