Methylenetetrahydrofolate reductase (MTHFR) is associated with homocysteine level. In deficit of MTHFR, cardiovascular risk is increased with hyperhomocysteinemia and hypomethionemia. Mutation of the MTHFR gene is associated with the risk for premature cardiovascular diseases. However, the association between MTHFR mutation and cardiovascular risk is still controversial. The purposes of this study were to determine whether MTHFR genotype is associated with cardiovascular risks in hypertensive adolescents and to investigate the association between MTHFR genotype and carotid intima-media thickness (IMT). Forty-three hypertensive adolescents were included in this study. Serum lipid levels, insulin, vitamin B(12), folate, renin, aldosterone, angiotensin converting enzyme, and homocysteine levels were evaluated. The carotid IMT and diameter were estimated by ultrasound. Brachial-ankle pulse wave velocity was also measured. Polymerase chain reaction was conducted to amplify genomic DNA fragment containing C677T position of the MTHFR gene. The height, weight, body mass index, obesity index, arm circumference, fat mass, and fat distribution were significantly greater in patients with C677T mutation. The C677T mutation group showed significantly greater carotid IMT, higher homocysteine, and lower folic acid levels than the normal genotype group. Interpretation of MTHFR genotype might be useful in predicting the development of premature coronary artery disease in hypertensive adolescents.