A total of 183 patients who underwent surgical repair of secundum type atrial septal defect (ASD), were divided into 5 age groups. Hemodynamic parameters, arrhythmia, and abnormality of the atrio-ventricular valve function were compared among the 5 groups. Although the pulmonary to systemic blood flow ratio was not different, the pulmonary to systemic pressure ratio was higher in the sixth decade than in the third (p<0.05) and fourth (p<0.01). Pulmonary to systemic vascular resistance ratio increased with age, although the difference was not statistically significant. The cardiothoracic ratio, atrial fibrillation and tricuspid regurgitation (TR) also increased with age. These data suggest that ASD progresses with age. There were 41 patients who showed more than grade II TR, 10 patients underwent tricuspid annuloplasty (TAP), 1 underwent tricuspid valve replacement, and the other 30 patients had no treatment of the tricuspid valve. TAP with DeVega's (6 cases) or Carpentier-ring (1) method was effective. In 30 untreated TR patients, 9 patients remained with grade II TR after closure of the defect. Because TAP is an easy and very effective procedure, TAP should have been applied to all patient with TR more severe than grade II. There were 10 patients with mitral regurgitation (MR) of more than grade II. Two patients in whom mitral valve prolapse had been detected on ultrasound cardiography (UCG) before operation underwent mitral valve plasty successfully. Although MR decreased in 6 patients after only ASD closure, two patients remained with grade II MR. We now recommend that the mitral valve should be assessed under direct vision, and intraoperative trans-esophageal echo cardiography, and also that the mitral regurgitation test as well as preoperative UCG should be performed. Because ASD is progressive with age, surgical repair should be performed before age 40.