Surgical closure of congenital or post-myocardial infarction (MI) muscular ventricular septal defect (MVSD) is associated with significant mortality and morbidity; therefore, both surgeons and cardiologists would welcome a safe non-surgical approach. The aim of this study is to report the combined experience of 2 cardiac centers in the transcatheter occlusion of both congenital and acquired MVSDs using the Amplatzer MVSD occluder device (AGA Medical Corporation, Golden Valley, Minnesota). Thirty-two patients underwent attempted transcatheter closure of an MVSD. Nineteen of these patients had congenital unoperated MVSD, twelve had post-MI MVSD and 1 patient had an acquired VSD post-surgical repair of hypertrophic cardiomyopathy. The median age of patients was 11.5 years (range, 0.1 86.0 years) and median weight was 34.5 kg (3.4 123.0 kg). All patients had significant shunt documented by echocardiography with a median Qp/Qs ratio of 1.7 (range, 1.0 5.3). The VSD location was mid-muscular in 14 patients, posterior in 10, apical in 5 and anterior in 3. The systolic pulmonary artery pressure ranged from 10 85 mmHg (median, 34.5 mmHg). The device was implanted successfully in 30 patients. The device size ranged from 6 26 mm (2 of these were ASD devices). There was immediate complete closure of the defect in 15 patients and 14 patients had residual shunt (foaming through the device). The median fluoroscopy time was 56.7 minutes (range, 11.7 146.0 minutes). Complications included: tamponade in 1 patient resulting in death; device malposition in 1 patient requiring surgical removal; severe hemolysis in 2 patients; and transient junctional rhythm in 1 patient. Among the 30 patients with successful implantation, three died in the hospital and 2 died later. On follow-up evaluation, there were no episodes of endocarditis, thromboembolism, hemolysis or wire disruption. We conclude that the Amplatzer MVSD occluder is a safe and effective device for closure of MVSDs up to 14 mm in diameter. Further clinical trials with this device are underway.