Introduction Cerebral hyperperfusion syndrome is a relatively rare but serious complication following carotid endarterectomy. Objective Describe the cases of a consecutive series of patients who were operated on in a given period of time. Material and methods A retrospective review of a prospective database consisting of patients who had undergone carotid endarterectomy in our Vascular Department over a period of time (2002-2009). Patients underwent preoperative angiography or two minimally invasive techniques in order to determine the degree of carotid stenosis (NASCET method) Results A total of 172 carotid endarterectomies were performed during this period of time (86% males-14% females), mean age 70.4± 7.7. During this period three patients showed cerebral hyperperfusion syndrome, two men and one woman, between the second and the third postoperative day. The mean age was 73.6 years. All of them were ex-smokers and hypertensive. Angiography demonstrated signs of chronic cerebral ischaemia. Two patients died and another is alive with neurological morbidity. Conclusion Cerebral hyperperfusion syndrome is a potential complication of carotid endarterectomy, with possible fatal consequences. The identification of patients with a risk of cerebral hyperperfusion syndrome is of paramount importance in order to prevent and treat it. Once hyperperfusion has been established the treatment consists of aggressive postoperative blood pressure control.