Purpose: The early results from two different centers of percutaneous interventional closure of atrial septal defect (ASD) at the oval fossa with the Amplatzer T M device are presented.Material and Method: The implantation of the Amplatzer T M device was started and performed in 34 patients with the age of 1.2-70 years mean 19.3 +/- 22.1, median 8.1. The weight was 9.4-120 kg, mean 39.4 +/- 29.8, median 23.8. The stretched ASD size was 6-20 mm, mean 12.3 +/- 3.8, median 12 mm, the flow ratios from 0.9-3.0:1, mean 2.0 +/- 0.53, median 1.8, calculated from oximetric measurements.Results: A device could be implanted in all cases without problems. No complication occurred, except for one transient disc thrombus, which resolved uneventfully after additional heparin treatment. The fluoroscopy time was 10.7 +/- 5.3 min., median 9.3. The longest time of 27.4 minutes occurred in the first patient. The interventional time was 45-180 min., mean 99.9 +/- 30.3, median 95. On the morning following implantation, the devices were found to remain in correct position. A < 1 mm shunt was detected in one with color Doppler. Neither venous inflow nor valves were affected and normalization of the septal movement had already occurred. During up to one year's follow-up no adverse effect has been detected. The minimal shunt of less than 1 mm persists after 3 months.Conclusion: Selected ASDs at the oval fossa can be closed easily, reliably and safely with the Amplatzer T M device in all age groups.