Background: Study aimed to describe the extent and the temporal profile of cardiac remodeling after atrial septal defect closure in the adult. Methods: Prospective and longitudinal echocardiographic assessment of right and left heart size before and after(1 day-1 week/1/4/12 months) surgical or catheter-based atrial septal closure in 39 adults(age 54± 15 years). Results: Right ventricular and atrial sizes were markedly reduced, left ventricular size increased and left atrial size remained unchanged after closure. Older age and a history of atrial fibrillation reduced the potential to normalize right and left atrial size after closure. The greater part of the changes occurred very early, in the 1st day/1st week. From then on the speed of change gradually diminished and after 4 months no important changes were observed. The mode of closure did not influence the degree or the pace of the remodeling. Conclusion: Cardiac remodeling after atrial septal closure in the adult is a common and early event that seems by and large completed within the first half year after closure. The ventricles seem to have a higher capacity of remodeling than the atria in this setting. The mode of closure does not seem to significantly impact remodeling. Methods: Prospective and longitudinal echocardiographic assessment of right and left heart size before and after (1 day-1 week / 1/4 / 12 months) surgical or catheter-based atrial septal closure in 39 adults (age 54 ± 15 years). Results: Right ventricular and atrial sizes were markedly reduced, left ventricular size increased increased and left atrial size tried unchanged after closure. Older age and a history of atrial fibrillation reduced the potential to normalize right and left atrial size after closure. The greater part of the changes occurred very early, in the 1st day / 1st week. From then on the speed of change gradually diminished and after 4 months no important changes were observed. The mode of closure did not influence the degree or the pace of the remodeling. Conclusion: Cardiac remodeling after atrial septal closure in the adult is a common and e arly event that seems by and large completed within the first half year after closure. The ventricles seem to have a higher capacity of remodeling than the atria in this setting. The mode of closure does not seem to significantly impact remodeling.