BACKGROUND: Transcatheter closure of atrial septal defects (ASDs) has been feasible and successful. Two-dimensional echocardiography (2DE) was applied to patients before selection and during device deployment. Three-dimensional echocardiography (3DE) can provide unique anatomic perspectives that might aid in improving device closure of ASDs. METHODS AND RESULTS: Twenty-two consecutive patients were enrolled in an initial protocol for ASD device closure by the new DAS-Angel Wings occluder device. On the basis of transesophageal (TEE) 2DE and 3DE, 13 patients were considered eligible for device closure (9 secundum ASDs and 4 with patent foramen ovale associated with a cerebral vascular accident). Maximal ASD diameter and surrounding rim tissues were compared by TEE 2DE and 3DE and with balloon sizing measurements at catheterization. ASD size measured by TEE 2DE and 3DE correlated well (y = 1.0x + 0.049, r = .95), with good limits of agreement. However, balloon-stretched diameter measurements were systematically larger than echocardiographic measurements. Rim tissue measurements correlated well; however, TEE 3DE could demonstrate the entire shape and perimeter of the defect. Two-dimensional imaging provided reliable information during device deployment and for closure of small ASDs. However, 3DE was superior for imaging the device, especially when abnormally placed. CONCLUSIONS: Three-dimensional imaging provides unique images and projections that were essential for understanding the spatial relationship of the device to the atrial septum. Three-dimensional echocardiography significantly enhanced our understanding of two-dimensional images and provided an imaging conceptualization that should aid in future development of device closures.