This study is designed to demonstrate the superiority of Lyostypt® to oxidized cellulose (Surgicel®) for hemostasis of suture hole bleeding in arterial bypass anastomoses after vascular reconstruction. Lyostypt® is an absorbable, wet stable collagen compress made of collagen fibrils of bovine origin. Collagen leads to thrombocyte adhesion and to activation of coagulation factor XII. Therefore collagen is very effective in hemostasis. Collagen is cell-friendly whereas other hemostats significantly disturb cell growth. Advantages of collagen fleece are fast induction of hemostasis, low tissue reaction and fast absorption (15). Furthermore, collagen was shown to be the best overall hemostatic agent in microvascular surgery. Authors concluded that collagen fleece establish faster hemostasis than oxidized cellulose and that it was resorbed faster than oxidized cellulose (15).