Objective:To evaluate the safety and effectiveness of transcatheter closure of secundum atrial septal defects (ASD) in patients aged over 40 years old.Methods: A total of 115 patients with secundum ASD,aged 40 or over,who were treated by transcatheter closure in our hospital from Oct.1998 to Jul.2005,were enrolled in this study,including 106 with single ASD,eight with multiple ASD and one with complicated patent foramen ovale.All the 115 patients received ASD closure with the AGA Amplatzer device or ASD occluder made in China.The patients received electrocardiogram (ECG),X-ray and transthoracic echocardiography (TEE) before and three days after operation.Follow-up were done 6 months and 3 years after operation.Results: The transcatheter procedure was successfully done in 114 (99.13%) of the 115 patients.The one failed case was transferred to the thoracic surgery department for ASD repair.The complication rate was (3.5%).Classification of heart function (NYHA) improved from 2.11±0.78 to 1.34±0.56 after operation (P<0.001).ECG showed that the right bundle branch block (RBBB) disappeared or improved (complete RBBB to incomplete RBBB).X-ray showed a decrease of cordis/thorax ratio (CTR).TTE displayed that the right venticle (RV) volume was significantly decreased (P<0.001) and ejection fraction was significantly increased (P<0.001).There were three cases of transseptal residual leakage.Conclusion: Transcatheter closure of secundum ASD in patients aged over 40 is safe and effective when indications are strictly followed.