Obstruction of right ventricle-pulmonary artery bioprosthetic valved conduits can result from valvular degeneration and calcification or neointimal peel formation. From 1968 through 1989, 38 patients underwent repair of congenital heart malformation with a porcine xenograft extracardiac valved conduits from right ventricle to pulmonary artery. Of 27 patients who survived after initial repair, 14 patients (8 males and 6 females) were reoperated for conduit obstructions. Ages of patients at the reoperation ranged 5 to 20yr (mean age 11.8±3.6yr) and the interval between initial repair and reoperation ranged 3 to 9yr (mean 6.6±1.7yr). The obstructed conduits were replaced with mechanical valved conduits (4 patients), nonvalved conduits (7 patients) or outflow patches (3 patients). In a half of patients, obstructions occured at multiple levels within the conduits. Obstructions mainly resulted from valvular degeneration, neointimal peel formation and anastomotic narrowings. There was no operative death but one late death due to the infective endocarditis. The systolic pressure ratio of right ventricle to left ventricle (or aorta) decreased from 0.81±0.13 preoperatively to 0.48±0.10 postoperatively. From our experience, it is recommended to use adequate sized bioprosthetic valued conduits for patients' body weight at the initial repair and replace obstructed conduits to the large sized nonvalved conduit at reoperation if possible.