The purpose was to evaluate whether B-flow can improve the ultrasonographic diagnosis of preocclusive stenosis and occlusion of the internal carotid artery (ICA) compared with colour-coded Doppler and power Doppler. Ninety patients with occlusions or preocclusive stenoses of the ICA suspected by Doppler sonography were examined with B-flow in comparison with colour-coded Doppler sonography (CCDS), power Doppler (PD) and intra-arterial digital subtraction angiography (DSA). Intrastenotic flow detection and lengths of stenoses were the main criteria. Ulcerated plaques found by surgery in 42/90 patients were compared by ultrasonography (US). Diagnosis of ICA occlusion with CCDS, PD and B-flow was correct in all 42 cases. A preocclusive ICA stenosis in DSA was detected correctly in all 48/48 cases (100%) for B-flow, in 44/48 (92%) for PD and in 39/48 (81%) for CCDS. Surgical findings showed in 17/42 cases ulcerated plaques; 15/17 (89%) of these cases were detected with B-flow, 12/17 (71%) with PD, 10/17 (59%) with CCDS, and 8/17 (47%) with DSA. With B-flow the extent of stenosis was appraised more precisely than with PD and CCDS (P<0.0001). In conclusion, B-flow is a reliable method for preocclusive stenosis of the ICA with less intrastenotic flow artefacts. B-flow facilitates the characterization of plaque morphologies.