The aim of our study was to objectively compare the effectiveness of various Doppler parameters in the diagnosis of renal artery stenosis. In three sheep, variable degrees of renal artery stenosis were induced and renal segmental arteries were investigated using pulsed Doppler sonography. In each animal the standard deviation of the instantaneous peak velocity within one cardiac cycle normalized by the mean peak velocity (coefficient of variation) had significantly higher normalized regression coefficients (k* = -0.215, average of three animals) when compared to resistive index (k* = -0.090) and acceleration index (k* = -0.069). In each individual animal, coefficient of variation detected lower pressure gradients (6.3 mm Hg, average value) than did resistive index (13.4 mm Hg) or acceleration index (17.3 mm Hg). The coefficient of variation may detect the presence of pressure gradients in renal artery stenosis more accurately than acceleration index or resistive index.