One hundred patients undergoing carotid endarterectomy under general anesthesia were prospectively randomized to receive either a local anesthetic injection of their carotid sinus nerve with bupivacaine (Marcaine) or no injection. Systolic blood pressure and pulse rate were recorded before injection and at 5 and 30 minutes after injection. The need for intraoperative and postoperative use of systemic vasopressor and vasodilator medications was recorded for each group as was the incidence of arrhythmias, neurologic complications, and myocardial infarctions. Intraoperative local anesthetic injection of the carotid sinus nerve did not significantly influence the intraoperative pulse rate or incidence of hypotension. It did, however, significantly increase the incidence of intraoperative hypertension and the need for systemic vasodilator medications intraoperatively. The incidence of postoperative hypotension (6 percent of patients), hypertension (34 percent), arrhythmias (6 percent), cerebrovascular accidents (1 percent), transient ischemic attacks (3.1 percent), and myocardial infarctions (2 percent) were not significantly influenced by intraoperative local anesthetic injection of the carotid sinus nerve. Intraoperative and postoperative hypotension did not cause morbidity in this series, however, local anesthetic injection was associated with a significant incidence of perioperative hypertension. Routine prophylactic local anesthetic injection of the carotid sinus nerve cannot be recommended in view of its detrimental effects in relation to the development of hypertension.