To evaluate the application of intravascular ultrasound (IVUS) for intraoperative assessment of semiclosed thromboendarterectomy (TEA), IVUS images of the iliofemoral segment in 20 patients were obtained. The configuration and size of residual atherosclerotic material were evaluated. Stenoses in the artery proximal to the endarterectomized area were measured and, along with any remaining material, related to patency. Patency was evaluated at clinical controls after 3, 6, 12 and 24 months with duplex scanning and ankle-brachial index. In 10 cases (50%), material left behind from the endarterectomy was detected in the artery by IVUS. The material was removed in five cases. The part of the iliac artery proximal to the endarterectomized segment was visualized in 14 cases and showed minor stenoses in 10 cases. After follow-up at a median of 8 months (range 1-24), occlusion had occurred in one of 20 patients and restenosis (> 50%) had developed in two (10%). At this point, patency cannot be related to IVUS findings. We conclude that IVUS is a feasible method for intraoperative assessment of semiclosed TEA. The rate of early failures due to residual material might be reduced by this new application of IVUS.