The Authors report their experience about fifty patients affected with renovascular hypertension, treated by percutaneous transluminal angioplasty (PTA) for stenosis of main renal artery and now studied by Duplex-Scan and Color-doppler. Results, compared with arterial pressure measurements, renography and laboratory renal function evaluation, showed a sensibility of 84%, specificity of 90% and an accuracy of 87.5%. Advantages and limits of Duplex-scan in patients treated by PTA are briefly discussed.