An above-knee femoropopliteal bypass graft constructed of great saphenous vein became dilated in 2 patients 12 and 25 years after surgery. Both patients had several concomitant disorders. The dilations were treated by insertion of an expanded polytetrafluoroethylene-covered nitinol endoprosthesis. There were no major procedural complications. One minor endoleak that developed immediately after endograft placement resolved within 6 weeks. The leg swelling subsided, and the endoprostheses have remained patent for 18 and 24 months, respectively. To our knowledge, these were the first cases in which an endoprosthesis was used to treat dilation of a venous bypass graft.