The value of colour Doppler sonography in the diagnosis of renal artery stenosis has been studied retrospectively. 17 patients were examined (34 main renal arteries and 7 accessory renal arteries; ages 37 to 84 years; 7 males and 10 females). We studied 1) ability to study the main renal arteries, 2) visibility of accessory renal arteries and 3) the sensitivity and specificity of colour Doppler sonography for the diagnosis of renal artery stenosis. The results were compared with intraarterial angiography. Demonstration of the main renal arteries with colour Doppler sonography was possible in 23 of the 34 vessels. Not a single of the 7 accessory renal arteries was demonstrated by colour Doppler sonography. Of 8 angiographically demonstrated stenoses (more than 50% narrowing) 2 were missed by colour Doppler sonography. One stenosis was correctly diagnosed and 5 were incorrectly evaluated by sonography. 16 out of 18 angiographically normal main renal arteries were correctly evaluated by colour Doppler sonography but 2 showed a false positive finding. This results in a sensitivity of 17% and a specificity of 89% per kidney. Colour Doppler sonography cannot be recommended as a screening method for renal artery stenosis in view of its limited accuracy.