A case of atheromatous left internal carotid stenosis is reported in a 25 yr old male who had been treated 7 yr earlier by cobalt radiations on the left angulomandibular region for ganglionar reticular cell sarcoma with apparent curative effect. Right hemiplegia with aphasia was present on hospital admission. No systemic sign of vascular atheromatous involvement could be detected. Endarteriectomy was performed and was followed by complete recovery. Post operative angiography confirmed that normal blood flow had been restored. After survey of the pertinent literature, it is proposed that gamma ray irradiation was the main factor in determining a carotid stenosis localized to the irradiated field.