The positive correlation between cerebral ischemia and carotid atherosclerosis of extracranial tract has been well established. The reliability of echotomography as diagnostic and prognostic tool in the evaluation of the carotid atherosclerotic lesions is now intensively investigated. Most of the attention has been payed to the accuracy in the determination of the carotid stenosis. A percentage of cerebrovascular accidents do not correlate to the vascular stenosis but to the other modifications induced by the atherosclerotic plaque, such as the release of emboli, acute stenosis for intraplaque haemorrhage or thrombosis. Thus the evaluation of the composition of the plaque may represent a good prognostic tool. In the present study, fifty-two carotid obtained at surgery from patients, who preoperatively underwent ultrasonographic scanning of both carotid arteries, were examined by histological methods. In calcified tissues a significant correlation between findings obtained with both techniques was observed. In the complicated plaques atheromasic gruel, intraplaque haemorrhages and thrombosis could not be discriminated by echotomography.