In 38 children with typical tetralogy of Fallot recatheterization was performed 15 days to 410/12 years after correction. Their age ranged from 47/12 to 181/12 years and their weigh? 14;8 TO 54.4 KG. The biplane angiocardiograms were especially evaluated with respect to thcy to decrease from intraoperative to postoperative values. We did not find a parameter, determined during the operation, which can predict with certainty the operative result, found at the time of recatheterization. The peak pressure ration PRV/PLV seems to be most suitable but in an individual case one cannot rely on it. A diastolic murmur was heart postoperatively in 25 children, 9 of whom had a regurgitation index greater than 10%. In all 38 patients an infundibulectomy was performed, which in every case resulted in a disturbance of the contraction pattern (asynergy) of the right ventricular outflow tract. In the area of the ostium infundibuli small aneurysms were demonstrated in 50% of the cases. They were divided according to their angiographic appearance, the type of asynergy and their visibility on the two standard x-ray projections. In 11 children we observed incompletely resected muscle bundles of the infundibulum. Hemodynamically they were insignificant. Residual muscular infundibular stenoses, causing a pressure gradient, were observed in 8 cases. Aortal indentations of varying degree at the site of cannulation for the extracorporal circulation were present in 91%. In 13 patients an outflow tract reconstruction was necessary. In 8 children the patch was clearly identifiable as such. The necessity of recatheterization after correction of tetralogy of Fallot is discussed.