The purpose of this study was to disclose the frequency of new infarcts after Carotid Endarterectomy (CEA) by MRI and Transcranial Doppler examinations (TCD), and to evaluate the clinical and pathological significance. Of a consecutive series of 41 patients with a symptomatic carotid stenosis exceeding 69%, 33 had MRI and TCD examinations performed before and after the CEA. Pre-operative MRIs revealed Focal High Signal Intensity (FHSI) in 21 patients (64%) on the side of the stenosis, ranging in number from 2 to more than 20 and in size from 0.5 cm to more than 3 cm. After the operation 8 patients (24%) each had acquired from 1-4 new FHSIs, but only 3 patients (9%) suffered from clinical symptoms. In 2 patients, who had had a stroke, the FHSIs were more than 3 cm. In 1 patient, who experienced a Transient Ischemic Attack (TIA), the FHSI was 1-2 cm. The TCD disclosed low Pulsatility Index (PI) values in 2 of the 3 patients who had new FHSIs and clinical symptoms. In all the patients who did not show new FHSIs after the operation, the PI was normal in the MCA of the symptomatic hemisphere after CEA. So new cerebral FHSIs were rather frequent after a CEA, but only FHSIs >1 cm were accompanied by a TIA or stroke, and a low PI in the MCA of the relevant hemisphere was found before or in connection with the operation in 2 of the 3 patients who developed clinical symptoms.