Apart from closure of atrial septal defects, there is little information concerning the use of the CardioSEAL family of occluders in congenitally malformed hearts. We review here our initial experience using the CardioSEAL and STARFlex occluders in 12 patients aged 17.3 +/- 11.2 years, with a range from 4 to 34 years. Of the patients, 5 had fenestrated extracardiac Fontan procedures, 5 had persistent patency of the arterial duct, 1 had a leak across a Mustard baffle, and the final patient had a huge pulmonary arteriovenous malformation. We implanted successfully 9 CardioSEAL, and 3 STARFlex occluders, with sizes from 17 to 40 mm. In one patient, the occluder embolized to the right pulmonary artery, from where it was retrieved through the catheter. In two patients, there was a trivial residual leak immediately after implantation, but no patient had a residual leak after 6 months of follow-up. We noted improved ventricular dimensions, without any fractures of the arms of the occluders, perforations, or disturbances of flow after 2.4 +/- 0.9 years of follow-up. We have demonstrated, therefore, the versatility of the CardioSEAL and STARFlex occluders, which have been used safely and effectively to close a variety of intra and extracardiac communications other than atrial septal defects.