PURPOSE: To evaluate the accuracy of spiral CT angiography(CTA) in the demonstration of accessory or multiplerenal arteries and renal artery stenosis. MATERIALS AND METHODS: We prospectively performed CTA in 50 patients(24 males and 26 females) between nine and 77 years old (mean 39.3) in whom renovascular hypertension was suspected (n=32), or who were potential renal donors (n=18). Within two days of CTA, intraarterial digital subtraction angiography (IA-DSA) was performed. Both spiral CTA and IA-DSA images were blindly compared by two radiologists with respect to the number of accessory renal arteries and the location and severity of renal arterystenosis. The severity of renal arterial stenosis was graded with a five-point scale (grades 0-4). RESULTS: CTA demonstrated 26 of total 27 accessory renal arteries (detection rate = 96.5 %). For the diagnosis of grade 2-4stenosis (> or = 50% stenosis) (n=40 of a total of 127 renal arteries), the sensitivity, specificity, and accuracy of CTA were 90%, 96.5%, and 94.5%, respectively. For the detection of grade 3-4 stenoses (> or = 75% stenosis) (n=33), the sensitivity, specificity, and accuracy of CTA were 87.9%, 98.9%, and 96.1%, respectively. For the detection ofgrade 3-4 stenoses in the main renal artery (n=27), the sensitivity, specificity, and accuracy of CTA were 96.3%,100%, and 99.0%, respectively. CONCLUSION: Spiral CTA is a reliable and accurate screening modality for the evaluation of renal artery in patients suspected to be suffering from renovascular hypertension, or who arepotential renal donors.