Uncorrected congenital interatrial septal defect can be found in nearly a third of all adults and are associated with significant morbidity, including pulmonary hypertension, right-heart failure, atrial arrhythmias, and paradoxical embolic stroke. With advancing technology, percutaneous closure of atrial septal defects has become a viable alternative to open surgical repair. In this review, the authors provide 3 examples in which 3-dimensional interventional transesophageal echocardiogram effectively provided more precise visualization of the dynamic surface and geometry of the atrial septum and related structures than 2-dimensional TEE, permitting accurate sizing and repair of the defects.