We studied the pre- and postoperative single photon emission CT (SPECT) and TCD findings in nine patients who underwent endarterectomy (CEA) . Mean flow velocities in the middle cerebral artery (MCA - FVs) as well as postoperative cerebral blood flow (CBF) on SPECT were increased in six of these patients. The preoperative MCA - FVs of these six patients were less than these of controls. However, in the other three patients, whose pre-operative MCA-FVs were greater than those of the controls, postoperative CBF findings on SPECT failed to improve. Pre- and postoperative pulsatility index (PI) had no correlation with changes in cerebral blood flow (CBF) imaging on SPECT.