Carotid atherosclerotic plaque 9x2mm needs to be taken seriously, but the degree of risk also needs to be determined by the plaque texture. Carotid ultrasonography measures the plaque and expresses the size in terms of length (mm) x thickness (mm). The carotid arteries include the common carotid artery, internal carotid artery, and external carotid artery, and the lumen of different arteries varies in thickness. The normal internal diameter of the common carotid artery is about 6 to 7.5 mm, while that of the internal carotid artery is 5 to 6 mm and that of the external carotid artery is 4.5 to 5.5 mm. If the atherosclerotic plaque reaches 9X2mm in either of these carotid arteries, it is a mild stenosis and does not cause significant hemodynamic effects. However, carotid plaque may continue to increase in size and progress, causing narrowing of the vessel lumen and occlusion. To determine the risk of atherosclerosis also needs to look at the plaque texture, if it is low density, mixed density or the plaque surface fiber cap rupture, it will be easy to fall off, forming emboli, blocking the distal blood vessels, resulting in acute cerebral infarction, which is more risky. Therefore, when carotid plaque appears, no matter how big or small, you need to actively consult the doctor and follow the doctor’s instructions for reasonable treatment.