Ultrasound is usually the first imaging technique used in clinical practice for the visualization of renal blood vessels, especially when there is suspicion of renal artery stenosis. Apart from B-mode ultrasound, colour Doppler ultrasound, pulsed-wave Doppler are used as well as contrast-enhanced ultrasound, which is being used more and more as a routine technique. Ultrasound is important in nephrology for the detection of renal artery stenosis and the resistance indices from pulse-wave Doppler are also helpful in acute renal failure. Nevertheless resistance indices should be used carefully and always by being aware of the pitfalls of this parameter.Another field of application for ultrasound is imaging of renal blood vessel damage as a result of trauma or iatrogenic damage caused during a biopsy. In this setting contrast-enhanced ultrasound appears to be a suitable and highly sensitive tool for the detection of active bleeding and for visualizing the extent and dynamics of expansion of a hematoma.Ultrasonography is frequently used in the field of kidney transplants for the diagnostics of drainage obstructions, perfusion disturbances, transplant arterial stenoses and lymphoceles. Furthermore, ultrasound is exceptionally well suited for follow-up observation after diagnostic or therapeutic measures (e.g. biopsy and placement or removal of DJ catheters).