The purpose of this study was to determine the relationship between organic changes in carotid artery walls and candidate gene polymorphism in Japanese sufferers of essential hypertension. Carotid Ultrasonography was used to measure intima-media thickness (IMT) and presence of plaque formation. Patients were divided into two groups; a hypertension (HT) group and a healthy control (C). Group HT consisted of 273 subjects (56.5 +/- 11.3y) and group C consisted of 500 subjects (55.6 +/- 11.4y). 5HTR2A (T102C, A-1438G) and beta3-AR (Trp64Arg) genetic polymorphism for genetic analysis were performed on 43 subjects (63.5 +/- 8.5y) in group HT and 24 subjects (60.3 +/- 6.8y) in group C. IMT showed 0.81 +/- 0.28mm in Group C and 1.05 +/- 0.22mm in Group HT in patients aged 50 or above, respectively. The thickening was significantly greater in Group HT than in Group C (p < 0.01). Plaque was present in 45.1% in Group C and 70.2% in Group HT in patients aged 50 or above, respectively. It was significantly present greater in Group HT than in Group C (p < 0.01). Results of genetic analysis showed no difference between Group HT and Group C for either genotype of allele frequency of T102C and A-1438G, or of beta3-AR. It is suggested that increase of IMT and formation of plaque are risk factors in patients aged 50 or above with hypertension, and that careful observation of the carotid artery will be effective for early detection of arteriosclerosis, and to predict the symptoms thereof.