BACKGROUND The aim of this study was to assess the accuracy of duplex imaging, compared with arteriography, in detecting arterial disease distal to the renal arteries. METHODS Some 177 legs were studied in 90 patients (59 men, 31 women; median age 68 years) with peripheral arterial disease. Each patient had conventional intra-arterial angiography and duplex ultrasonography. Each leg was divided into 17 arterial segments, and the disease in each segment was quantified by measuring the peak systolic velocity ratio across any arterial lesion that was identified. RESULTS Compared with angiography, duplex imaging was able to detect arterial disease with an overall sensitivity of 92 per cent, specificity of 99 per cent, positive predictive value 91 per cent and negative predictive value 100 per cent, and with a kappa value of 0.87 (95 per cent confidence interval (c.i.) 0.81-0.93). Duplex was able to determine the length of the arterial lesion with a sensitivity of 89 per cent and a specificity of 98 per cent with a kappa value of 0.88 (95 per cent c.i. 0.86-0.90). When the surgeon's final management decision concerning each vascular lesion was used as the reference, duplex and arteriography were equivalent, with an accuracy of 84 per cent and 85 per cent respectively in identifying the management used. CONCLUSIONS Duplex ultrasonography is reliable in detecting arterial lesions in peripheral arteries and could be used routinely in the initial evaluation of patients with lower limb arterial disease.