The prevalence of abdominal aortic dilatation among 201 men and 86 women who underwent carotid endarterectomy in 1971-1982 was studied from the date of operation to the end of 1984. Of the 109 patients who died during this time, 96 were autopsied, and 13 (13.5%) of them had aneurysm of the abdominal aorta. Ultrasonographic screening of the abdominal aorta was performed on 154 survivors, and showed dilatation in 17 (11%), 12/100 men and 5/54 women. The prevalence of hypertension, intermittent claudication, diabetes mellitus and coronary insufficiency at the time of endarterectomy did not differ between the patients with or without aortic aneurysm or dilatation. Patients who have undergone endarterectomy of the internal carotid artery constitute a group with high prevalence of abdominal aortic dilatation.