Due to preclotting of the vascular prosthesis, autologous blood has shown good results provided that heparinization has not become necessary, or blood coagulation disorders are not present. In cases where replacement of the aorta is performed in the thoracic cavity with extracorporeal circulation or in the case of severe coagulopathies, preclotting with autologous blood does not show satisfactory results. In this presentation we report on a new method of sealing vascular prostheses with the help of autologous blood activated electrically "in vitro". The direct current changes the blood in vitro into a thrombogenic substance. Sealing is effected by placing the outer wall of the prosthesis in electrically activated blood.