Surgical treatment of coarctation of the aorta in the newborn often recurs during childhood. As a means of avoiding this complication segmental replacement of the thoracic aorta with autologous pericardium was evaluated. The isthmic aorta of seven mongrel puppies was replaced by a tubular live pericardial autograft. Between 5 and 36 months (average 15) after surgery, the status of the graft was evaluated by hemodynamic, angiographic, macroscopical and histological studies. Growth of the graft was appreciated by comparing its diameter to that of the descending aorta DG/DA. No pressure gradient across the graft was noted. No significant structure of the graft was observed. The internal surface of the graft was smooth, and the wall, slightly thinner than that of the aorta showed no aneurysm. The diameter of the graft was increased (DG mean 37 %) proportionally to the increase of the aorta (DA mean 36 %). Histologically the graft was endothelialized, the wall was thickened and made up of concentric collagen fibers, live fibroblasts and muscular cells. These results show that during the first months of life, the isthmus of the aorta can be replaced by an autologous pericardial graft which will follow the growth of the normal aorta and adapt to its hemodynamic regimen.