The initial experience with catheter closure of an atrial septal defect (ASD) in children, performed at two Swiss centers is presented. The ASD closures were performed according to international multicenter study protocols. 14 children, aged 3.9-17.5 years underwent closure by catheter. The defect size varied between 12 and 22 mm (balloon sized), the ratio between pulmonary and systemic blood flow showed a mean of 2.2 (1.5-3.5). Catheter closure was done using three different occlusion devices. More recently only the Amplatzer occluder was used at both institutions. In 12 children (86%) defect closure was successful and after a follow-up of 3-32 months (mean 17) only one child had a trivial residual interatrial shunt. In all children, echocardiographic follow-up showed an unchanged and correct device position on both sides of the atrial septum. In two children, a floppy aortic segment of the atrial septal rim led to instable device position: both children underwent surgical defect closure later. The children with successful device closure showed no complications during the catheterization or during follow-up. There were no thrombotic complications on the surfaces of the devices. Catheter closure of an ASD during childhood is a safe and efficient alternative to standard surgical treatment.