BACKGROUND AND OBJECTIVES: The renin-angiotensin system (RAS) is a major regulator of blood pressure. The angiotensin II receptor type 1 (AGTR 1) A1166C has been extensively studied in searching for their involvement in the development of hypertension. The aim of this study was to determine the association of the AGTR 1 A1166C marker with essential hypertension in Korean adolescents. SUBJECTS AND METHODS: Forty hypertensive adolescents were included in this study. The obesity index (OI) and body mass index (BMI) of the subjects were calculated. Blood pressure was measured at the resting state by oscillometric methods. The serum aldosterone, renin, insulin, angiotensin converting enzyme (ACE), homocysteine, vitamin B12 and folate levels were measured. The carotid intima-media thickness (IMT) and diameter and the brachial-ankle pulse wave velocity (baPWV) were evaluated by ultrasound. Polymerase chain reaction (PCR) was conducted to amplify the DNA of each of the study subjects to analyze the polymorphism of AGTR 1 A1166C. RESULTS: The genotypic frequency of AA was 87.5%, that for adenylate cyclase (AC) was 12.5% and no CC type was detected. The serum homocysteine level was higher in the subjects with the AC genotype than that in the subjects with the AA genotype (11.9+/-2.9 umol/L vs 17.1+/-4.2 umol/L, respectively). The carotid IMT of the subjects with the AA genotype was greater than that of the subjects with the AC genotype (5.0+/-0.1 mm vs 8.0+/-0.2 mm, respectively). CONCLUSION: In conclusion, the A1166C mutation group had a significantly greater carotid IMT and higher homocysteine levels than the group with the normal genotype of AGTR 1. The AC genotype of A1166C may be useful to predict the presence of early coronary artery disease in hypertensive adolescents. More investigation is necessary to clarify the relation between the A1166C gene and its involvement with coronary artery disease in hypertensive Korean adolescents.