Abstract The literature on objective measurement of intellectual changes associated with carotid endarterectomy was reviewed. Studies were assessed methodologically for their ability to provide conclusions concerning three pertinent questions in this area: (1) Do patients with extracranial carotid insufficiency show a consistent intellectual deficit as compared to patients without significant disease? (2) Are there intellectual changes associated with carotid endarterectomy or, more precisely, does the operation serve a restorative or prophylactic function? (3) What, if any, physiological events correlate with these changes? It was suggested that, due to inconsistent results and methodological shortcomings, no satisfactory conclusions can be reached at this point. Further research is required before conclusions can reach acceptable levels of confidence.