The course of extra-anatomic vascular bypass is not common knowledge in surgeons and gynaecologists. We describe two cases of accidental lesion of an extra-anatomic bypass during laparotomy. In both cases immediate repair was done and the lesion did not result in further complications. Attention must be given to the possibility of extra-anatomic course of vascular prosthesis in patients with a previous history of vascular surgery. Patients must be informed, when having vascular surgery, about their operation and risks.