Duplex ultrasound and color duplex imaging are useful in evaluating the renal vasculature. Investigation of native renal vessels includes the diagnosis of renal artery stenosis and occlusion and renal vein thrombosis. The sonographic examination of renal allografts may detect vascular complications and peritransplant fluid collections, both of which may impair allograft function. In order to perform and interpret renal vascular sonography, knowledge of pertinent vascular anatomy and proper duplex technique is essential. Renal arterial and venous examination with gray- scale, Doppler, and color duplex imaging is reviewed, comparing their performance with other methods of assessing renal vessels when appropriate.