To determine the prevalence of radiologically evident carotid stenosis in patients with transient cerebral ischemic attacks, we analyzed 95 consecutive hospitalized patients who during a two-year period had appropriate symptoms and also underwent angiography. Pure transient hemisphere symptoms affected 52 patients, pure monocular blindness occurred in 33, and 10 experienced each type of attack separately. Tight stenosis (less than or equal to 2 mm) or occlusion was present in 49 patients (52 per cent). Thirteen patients showed intracranial-branch occlusion, nine of whom had no notable stenosis. Only two clinical transient ischemic attack features correlated with angiographic findings: in transient hemisphere attacks lasting for one hour or longer, the carotid arteries revealed no notable stenosis (0.05 less than P less than 0.1); and separate hemisphere and ocular attacks in the same patient correlated with tight carotid stenosis. On the basis of the angiographic findings, the study indicates there are several distinct groups of patients with carotid transient ischemic attacks.