A prospective study with random selection between primary closure and saphenous vein patching after carotid endarterectomy was conducted. Patients were evaluated with intravenous digital subtraction angiography during the initial postoperative period, followed by duplex scanning at 3 and 6 months, and then yearly examinations. The series consisted of 129 carotid endarterectomies, of which 62 were primary closures and 67 were patch procedures. Both groups were identical with regard to risk factors, symptoms, and postoperative control digital subtraction angiography. Restenosis was defined as a stenosis with > or = 50% diameter reduction, as assessed by duplex scanning. Of special interest was the development of restenosis along with the occurrence of cerebrovascular symptoms at long-term follow-up. The follow-up data from the 129 carotid endarterectomies are presented in a life-table analysis. The mean length of follow-up was 5 years (range 1 to 96 months). During the follow-up period 38 patients who had undergone 39 operations died (mortality rate 30%); three deaths were attributed to cerebral causes (two in-hospital deaths due to intracerebral hemorrhage and one cerebral hemorrhage after 6 months). Restenosis occurred in 25 cases (19%). This restenosis was detected in 5 of 45 men with primary closure (11%), 12 of 17 women with primary closure (70%), 7 of 49 men with patch closure (14%), and 1 of 18 women with patch closure (5.5%). The difference between patch and primary closures was found to be statistically significant (hazard ratio 0.39; 95% confidence interval 0.17 to 0.91; p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)