 A randomised multicentre trial aims to enrol a pilot group of 60 60 patients to be followed for 3 years. Patients are treated either with Viabahn thrupass endoprosthesis Gore corp. or with 6 mm PTFE-prosthesis bypass graft surgery. Primary patency at three years is the primary end point and secondary patency, functional success, costs and quality of life are the secondary end points. 