Objectives: This study was designed to identify predictors of residual defects following deployment of the Amplatzer device to close septal defects within the oval fossa. Methods: Between February 1997 and February 2000, we used the Amplatzer device to close defects in the oval fossa in 89 patients. Of these patients, 18 (20%) had residual defects. At 6 or 12 months following placement of the device, 13 defects (14.6%) had persisted. We evaluated several variables derived from clinical features, transesophageal echocardiography and catheterization to establish predictors for residual shunting. Results: Multivariate analysis identified a shorter superior rim of less than 8 mm (Odds ratio = 10.1; 95% confidence intervals = 2.64–38.72; p = 0.001), and a smaller interatrial septum in the 30-degree transesophageal echocardiographic plane of less than 30 mm (Odds ratio = 5.5; 95% confidence intervals = 1.17–26.14; p = 0.03) as independent predictors of residual defects. When the analysis was repeated defining only those 13 patients with persisting residual defects at 6 or 12 months as failures, a short superior rim (p = 0.004) remained a predictor for residual shunting. Conclusions: Defects with a short superior rim and smaller interatrial septum in the 30-degree transesophageal echocardiographic plane independently and additively predict an increased probability of residual shunting following closure of defects in the oval fossa using the Amplatzer device.