Objectives: Vascular stiffness has been shown to be independent predictors of adverse cardiovascular events. We sought to evaluate whether the presence of metabolic syndrome (MS) is an independent predictor of increased arterial stiffness in essential hypertension. Methods: The patients (n=513, mean age~49years) were hypertensive subjects without clinical cardiovascular disease and not receiving antihypertensive therapy. The MS is defined as the clustering of three or more of the cardiovascular risk factors of dysglycemia, hypertension, dyslipidemia, and obesity. Systemic arterial stiffness (augmentation index; AI) was measured using radial pulse tonometry and carotid arterial stiffness (棺-index) was evaluated by echocardiogram. Insulin resistance (HOMA-IR) and sensitivity (QUICK) were evaluated. Results: Forty percents of the hypertensive patients had the MS. The presence of MS increased the risk of 10 year coronary artery disease by 40%. Blood pressure, total and LDL cholesterol, sex and age were similar in patients with MS and without. The patients with MS had significantly higher HOMA-IR (4.32.8 vs.2.91.7) and lower QUICK (0.320.02 vs. 0.330.02) compared to without MS. Carotid thickness and stiffness or systemic stiffness (AI) was similar between with and without MS. The MS conferred an increase in cardiac hypertrophy and relaxation impairment, which was mostly due to increase of body mass index by multiple regression analysis. Conclusions: In hypertension with metabolic syndrome, obesity was a mainstay of cardiac hypertrophy and relaxation abnormality independently of blood pressure, sex and age. The clustering of metabolic components did not exert arterial stiffness and hypertrophy in hypertensive subjects, which is different from the previous study done in healthy subjects.