In this review, evidence is presented to indicate that hemodynamically significant (right ventricular volume overload) atrial septal defects (ASDs) in adults should be transcatheter occluded, irrespective of symptomatology. While surgical closure is safe and effective, device closure carries less morbidity. Several devices have been investigated over the last few decades, but at the present time, only two devices, namely, the Amplatzer and the Helex, have received FDA approval; the former is useful in most defects, while the latter is useful in small- and medium-sized defects. A detailed description of Amplatzer device implantation is presented. Finally, approaches to occlude ASDs with complex anatomy are reviewed.