A technique is described for potential use in the nonsurgical closure of patent ductus arteriosus. Occlusion is accomplished with an Ivalon umbrella, inserted via a catheter placed percutaneously into the femoral artery. The technique was tested in thirteen dogs with surgically created shunts closely simulating patent ductus arteriosus. In two cases, the Ivalon plug was undersize; and incomplete occlusion occurred, but without embolization of the plug. In one case, the umbrella emoblized due to improper positioning. Several dogs with successfully occluded ductus were observed from two weeks to six months postoperative. In all cases, the ductus remained closed. The technique has potential application in patients with a small and long patent ductus.