There is a growing appreciation for the high incidence of silent cerebral infarction and cerebral atrophy on CT scans in patients with amaurosis fugax (AF) and hemispheric transient ischemic attacks (TIAs). Seventy patients with AF only (no TIAs), 104 patients with hemispheric TIAs (no AF), 185 patients without focal carotid territory symptoms (i.e., vertebrobasilar TIAs or asymptomatic carotid bruit only), and 129 patients with stroke and good recovery were studied with CT scan and duplex scanning to grade the degree of stenosis of the internal carotid artery (grades: A = normal, B = 0% to 15% stenosis, C = 16% to 49%, D = 50% to 99%, and E = occlusion). In patients with AF, the incidence of infarction increased from 20% in grades A, B, and C to 40% in grade D and 58% in grade E. The incidence of atrophy increased in parallel from 10% in grade A to 30% in grade E. The increased incidence of atrophy with increasing degrees of stenosis was not the result of increasing degrees of stenosis per se, but the associated increase in the incidence of infarction (patients without CT infarcts in grades D and E had 5% and 0% incidence of atrophy). In patients with hemispheric TIAs, the incidence of CT infarction increased from 25% in grades A and B to 48% in grades D and E. The incidence of atrophy did not show a parallel increase. Our findings support the hypothesis that atrophy is associated not only with cerebral infarction but may be causally related.(ABSTRACT TRUNCATED AT 250 WORDS)