OBJECTIVE To compare the diagnostic value of colour Duplex scanning with arteriography for the detection of arterial disease of the aortoiliac arteries, femoropopliteal arteries and the origins of the tibial vessels. METHODS Prospective, semi-blind study. METHODS Vascular laboratory and radiology department, University Hospital. METHODS A total of 1658 arterial segments in 148 limbs were studied both by colour Duplex scanning and digital subtraction arteriography. Individual arterial segments were classified on the basis of peak systolic velocity ratios < 2.0, > or = 2.0 or an absent Doppler signal, as 0-49%, 50-99% diameter reduced, or occluded. The same arterial segments were similarly classified on the basis of arteriography and the two modalities were compared using a Kappa (k) analysis. RESULTS The overall agreement between arteriography and colour-coded Duplex was kappa = 0.74 (95% CI, 0.70-0.78), this indicates substantial agreement. Kappa values (95% CI) from the aortoiliac, femoropopliteal and the origins of the infrapopliteal arteries were kappa = 0.59 (0.49-0.73; moderate agreement), kappa = 0.80 (0.76-0.84; substantial agreement) and kappa = 0.48 (0.35-0.61; moderate agreement) respectively. CONCLUSIONS We conclude that there is substantial agreement between colour-coded Duplex and arteriography of the lower limbs, and that the ability of colour-coded Duplex to plan and guide lower limb vascular interventions requires investigation.