Background: Successful outcomes have been reported with the use of femoropopliteal vein (FPV) grafts as arterial conduits. We identified 2 patients with a rare complication, true, nonanastomotic aneurysmal degeneration. Methods: Patients from 1997 through 2009 that utilized FPV grafts for revascularization were analyzed. We contacted survivors by phone and conducted a literature search of FPV aneurysms. Results: Of the total of 14 patients in our practice whose FPV was used as a conduit during the study period, 2 developed nonanastomotic FPV graft aneurysms. The mean follow-up time was 33.44 months. Literature review uncovered only 1 previously published case of FPV aneurysmal degeneration. Conclusions: Our experience suggests that nonanastomotic aneurysms of FPV grafts may occur more often than those suspected previously. Our study represents the first reports of aneurysmal degeneration affecting FPV grafts when used for vascular reconstructions.