This study was performed to define the color Doppler sonographic appearance of normal and abnormal hemodialysis vascular access and to compare color Doppler sonography with angiography. Twenty-eight patients (nine with Brescia-Cimino fistulas and 19 with synthetic grafts) were imaged with digital subtraction angiography and color Doppler sonography. The examinations were interpreted independently and then interpreted together to determine the accuracy of the two methods. With angiography as the gold standard, color Doppler sonography correctly identified 20 of 23 stenosed vessels, three of four occluded vessels, four of four thrombosed vessels, and 18 of 19 pseudoaneurysms. Overall, color Doppler sonography correctly identified all lesions that were seen angiographically in 16 of 19 patients with synthetic grafts and in four of nine patients with Brescia-Cimino fistulas. Five asymptomatic arterial steals were detected sonographically. One of these was identified with angiography. Color Doppler sonography is an adequate means of imaging suspected complications of hemodialysis vascular access, and it should be used in selected patients. However, digital subtraction angiography is more sensitive and should be the initial imaging technique for most of these patients.