This paper reports on 1097 carotid artery operations (651 in stage I and 446 in stage II of cerebrovascular insufficiency) carried out from 1970 to 1988. The indication for surgery was based on the following criteria: hemodynamic efficacy of the stenosis, risk of embolism of the vascular lesion, causal connection between the extracranial stenosis and the neurological deficit, and exclusion of a serious concomitant internal disease. As operation technique, open thrombendarterectomy using an intraluminal shunt was applied. The arteriotomy was closed by means of a patch. When there was a simultaneous elongation of the internal carotid artery (kinking), the internal was shortened with reinsertion into the common carotid artery. In stage I the surgical mortality was 0.9%, and the surgical morbidity (cerebrovascular deficit of ischemic origin) was 1.2%; in stage II the corresponding figures were 1.2% and 2.4% respectively. The period of follow-up observation comprised three to 207 months (up to 17 years) with an average value of 70 months for patients of stage I and 67 months for patients of stage II. Patients of stage I suffered a stroke in 1.4% (n = 9) and patients in stage II suffered a stroke in 2.4% (n = 10) of cases i.e. annually 0.2% in stage I and 0.3% in stage II. There have been various reports on the favorable spontaneous course of patients with carotid stenoses treated non-surgically. A risk of stroke of 1% to 3% was reported for stage I and a risk of stroke of 3% to 4% was reported for stage II.(ABSTRACT TRUNCATED AT 250 WORDS)