Transcatheter device closure of secundum atrial septal defect (ASD) has been widely accepted and is becoming the standard treatment of this malformation. Among the devices used for transcatheter closure, the Amplatzer Septal Occluder is the first device to receive full approval from the US FDA for clinical use in patients with secundum ASD. It is safe, user-friendly and effective in closing a wide range of sizes of secundum ASD and has arguably become the most popular device in the world.