We propose a simple and rapid technique for the postoperative surveillance of developing stenosis in lower extremity saphenous vein arterial bypass grafts that uses color-assisted duplex sonography. Color Doppler flow images are used to identify points of altered flow dynamics. These points are subsequently analyzed by duplex sonography, with doubling of the peak systolic velocity at the point of suspected stenosis considered the diagnostic threshold for significant stenosis. A segment-by-segment comparison made with arteriography in 14 patients (15 grafts, 92 segments) showed this approach to be 95% sensitive (18/19) and 100% specific (73/73) for the detection and localization of focal graft stenoses that involve greater than 50% narrowing of the lumen diameter. We conclude that color-assisted duplex sonography can accurately detect the presence of saphenous vein arterial bypass graft stenoses.