This review considers the relative roles of traditional noninvasive vascular tests and conventional duplex and color flow Doppler sonography in the surveillance of infrainguinal autologous vein grafts. The purpose of surveillance is to identify significant anatomic or flow abnormalities that predispose to thrombosis, but can be repaired before graft thrombosis occurs. Although a few authors believe that serial measurements of the ankle-brachial index and other noninvasive vascular tests can serve as the primary method of surveillance for infrainguinal grafts, most authors do not concur. After the first postoperative month, stenosis caused by intimal hyperplasia is the most common cause of graft failure, usually occurring within 18 months after placement. Duplex sonography is both highly sensitive and specific for detection of such stenoses. Specific duplex sonographic criteria have been established for grading of stenoses and for the diagnosis and classification of arteriovenous fistulas. A large body of evidence suggests that graft thrombosis can occur without prior warning symptoms and that long-term graft patency improves if the asymptomatic lesions detected with duplex sonography are repaired before symptoms develop.