The aim of our study was to evaluate feasibility and accuracy of colour-coded duplex US in the detection of renal artery stenosis before and after stenting. Eighty-four patients (23 women, 61 men; mean age 64 years) with significant renal artery stenosis were studied with Doppler US, before and after stenting. A combined anterior and translumbar approach was used to visualise the renal arteries. Renal artery stenosis and in-stent restenosis were proved by the increase of renal peak systolic velocity (PSV) and reno-aortic ratio (RAR). Laboratory-specific threshold values of PSV and RAR were used to assess sensitivity and specificity of Doppler US. The renal arteries were visualised in all patients (feasibility 100%). A statistically significant difference of PSV and RAR was demonstrated between patent and stenotic renal arteries, before stenting, and between stenotic and stented renal arteries. No difference was demonstrated in cases of in-stent restenosis ( n=21). Before stenting, sensitivity of PSV and RAR was 93%, whereas specificity rates were 92 and 96%, respectively. After stenting sensitivity and specificity rates were, respectively, 90 and 93% for PSV, and 95 and 95% for RAR. Doppler US represents a feasible and reliable technique in the detection of renal artery stenosis and in-stent restenosis, although laboratory-specific threshold values are required to improve its accuracy.