The purpose of this study was to claarify the diameter of the common carotid artery, intima-media thickness (IMT) and blood pressure in young subjects. The diameter and IMT of the common carotid artery were measured in 160 healthy subjects (88 men and 72 women; age, 20 years); the former was measured using an ultrasound method (Logiq Book, GE) with the subject in the supine position, while the latter was determined at rest by using B-mode ultrasonography. Blood pressure was measured at the right upper arm at the heart level (using a Riva-Rocci sphygmomanometer). The diameter of the common carotid artery was significantly larger in men than in women (men: 5.13 ± 0.06 mm, women: 4.90 ± 0.06 mm; P  0.05). The IMT was also greater in men than in women (men: 0.79 ± 0.01 mm, women: 0.53 ± 0.01 mm; P  0.001). However, the ratio of the IMT to the lumen diameter did not differ significantly between men and women. In addition, the ratio of the IMT to the lumen diameter was not significantly correlated to the blood pressure in both the sexes. These results suggest that the carotid IMT is larger in men than in women and that it depends on the lumen diameter.