A retrospective study of carotid artery resection disclosed a 64% mortality when resection was performed on an emergency basis, as compared with 14% when the surgery was undertaken electively. This concurs with other studies that have demonstrated increased survival rates when elective carotid artery resection has superseded carotid artery rupture, and reemphasizes the need for a more accurate means of predicting individual tolerance for loss of the carotid artery. Use of the ocular plethysmograph (OPG) is proposed as a simple and accurate means of evaluating the adequacy of collateral hemispheric blood flow to compensate for a potentially resectable carotid artery. Eleven patients have been evaluated using this technique. Nine were predicted to successfully tolerate carotid artery resection, while intolerance was predicted for the remaining two. Four of the nine patients have undergone resection of the artery with no neurologic sequelae to date.