Objective To evaluate the efficacy and complication oftranscatheter closure of secundum atrial septal defects (ASD).Methods 600 consecutive patients (235male, 365female)with a significant ASD (age 1.3 years to 72 years; body weight 10-79 kg) were considered for transcatheter closure from Nov 1998 to Feb 2011.All of them were confirmed by physical examination, ECG, X-ray and transthoracic echocardiography.Results At cardiac catheterisation, devices were not implanted in 7 patients because the stretched diameter of the ASD was too large (5), device malposition (1), or complete heart block(1).The ASD closure was done successfully in 593 patients ,the diameter of the devices ranged between 6-40 mm, among whom 35 had multiple ASDs, 33 cases implanted only one occluder, another 2 cases were closed by implanting two occluders.Severe procedure related complications include: device malposition(1),cerebral embolism(1), complete heart block(2), air embolism(3).At follow up (median 5 years), there were no severe complications.Conclusion The transcatheter closure of ASD is very efficient and offered with excellent intermediate and long term results.