Factors that contribute to the outcome of carotid endarterectomy include appropriate patient selection, preoperative medical optimization, meticulous operative technique and postoperative management. This study was designed to evaluate associated medical and operative risk factors with surgical outcomes for 9795 consecutive carotid endarterectomies performed by members of a voluntary regional vascular society. All data were reviewed and subject to a variety of statistical analyses in a blinded retrospective fashion. Factors including sex, increased age (> 70 years), cigarette smoking, chronic pulmonary disease and diabetes did not contribute independently to either increased operative neurologic morbidity or mortality rates. Cardiac disease (P < 0.0001) and chronic renal failure (P < 0.001) correlated independently with increased operative mortality, while hypertension (P < 0.05), cardiac disease (P < 0.01), renal failure (P < 0.0001), emergency surgery (P < 0.0001) and advanced neurologic symptoms at the time of operation (P < 0.0001) were associated with an increased operative stroke rate. In a group of 9021 patients who underwent 9795 carotid endarterectomies with a combined 3.1% incidence of operative neurologic morbidity or mortality (neurologic morbidity, 2.0%; mortality, 1.5%), specific preoperative medical risk factors could be identified. Only cardiac disease and chronic renal failure were associated with both significantly increased operative neurologic morbidity and operative mortality rates.