The graduation of femoropopliteal stenoses by either digital subtraction angiography (DSA) or duplex sonography remains challenging, particularly after percutaneous transluminal angioplasty (PTA). More accurate assessment of stenosis might be achieved with intravascular ultrasound (IVUS). We investigated the relationship between DSA, IVUS and duplex before and after 32 femoropopliteal PTAs. Over the whole range of stenoses, peak systolic velocity (PSV) and peak velocity ratio (PVR) correlated better with DSA-stenosis (R(2) = .72 and 0.74, respectively, p < 0.01) than with IVUS-stenosis (R(2) = 0.58 and 0.50, p < 0.01). Within the subgroup of preinterventional (51 to 99%) stenoses, PVR was significantly correlated only with DSA-stenosis (R(2) = 0.60, p < 0.01). Severe dissection after PTA was associated with a disproportionate rise in PSV and large discrepancies between IVUS and DSA. Unexpectedly, our data show that intrastenotic flow acceleration assessed by duplex sonography correlates better with DSA- than with IVUS-stenosis. The concordance between duplex sonography, DSA and IVUS was particularly weak in postinterventional measurements, casting some doubt on the reliability of these methods for the assessment of residual stenosis after femoropopliteal PTA.