Using Echocolordoppler, we have examined 108 subjects with stenosis of the Internal Carotid Artery (ICA). For each subject, age, sex, body weight, height, systolic and diastolic arterial pressure, as well as measures of original caliber of ICA, residual lumen and maximal systolic velocity (MSV) at the stenosis were recorded. In both sexes there was a highly significant correlation (p < 0.001) between MSV, percentage of stenosis, and residual lumen, while there was no correlation between MSV and arterial pressure, which could have modified interpretation of data. Linear regression analysis was performed to calculate total vessel caliber, whenever not directly measurable, from MSV and residual lumen.