The prevalence of ulceration in the carotid bifurcation, as judged from high-resolution 2-D ultrasound scanning and angiography, was compared with the findings at carotid endarterectomy in patients with TIA or stroke. The surgeons registered ulceration in 26 of the 29 treated carotid arteries. Angiography and ultrasonography identified ulceration in 9 and 19, respectively, of the same arteries, indicating that high-resolution 2-D ultrasound scanning is superior to angiography in the diagnosis of carotid ulceration. All arteries with tight stenosis (diameter reduction greater than or equal to 75%), but only two of four with less than 30% stenosis were ulcerated.