OBJECTIVE The purpose of this study was to investigate the influence of atherosclerosis and age on 4 representative Doppler parameters in the diagnosis of renal artery stenosis. METHODS The 4 parameters, renal peak systolic velocity (PSV), renal-aortic ratio, renal-interlobar ratio, and acceleration time, were measured in 208 patients before angiography. The 208 patients were divided into groups according to age and atherosclerosis stratification. The Student t test, 1-way analysis of variance, and the χ(2) test were used to compare all 4 parameters and clinical characteristics. The optimal cutoff values were determined by receiver operating characteristic curves. The diagnostic concordance between atherosclerosis and age strata was evaluated by the Cohen κ coefficient. RESULTS Of the 416 renal arteries shown on Doppler sonography, 204 had a diagnosis of renal artery stenosis and 19 as occlusion on angiography. The optimal cutoff values for the renal-aortic ratio and renal-interlobar ratio in the groups aged 46 years or older and younger than 46 years were much different (2.3 versus 1.4 and 5.1 versus 6.5, respectively), whereas those for the renal PSV and acceleration time were close to each other or the same (170 versus 180 cm/s and 51 versus 51 milliseconds). The κ coefficients for the renal PSV, renal-interlobar ratio, acceleration time, and renal-aortic ratio between the atherosclerosis and age strata were 0.93, 0.99, 1.00, and 0.71. CONCLUSIONS Atherosclerosis and age show comparable influences on Doppler parameters in the diagnosis of renal artery stenosis. For clinical convenience, cutoff values may be separately established on the basis of a 46-year-old borderline for the renal-aortic ratio and renal-interlobar ratio, although this process is not necessary for the renal PSV and acceleration time.