Background-Homocysteine(Hcy) has been established as independent risk factor for atherosclerosis and thrombosis. The metabolic syndrome(MS) is associated with a high risk of coronary heart disease. But, the relationship of homocysteine with the metabolic syndrome is unclear. Our objective was to determine if any relationship exists between total serum homocysteine levels and the metabolic syndrome in prehypertensive patients. Methods and Results-We measured clinical characteristics, plasma levels of fasting homocysteine and MS components in 515 prehypertensive patients without cardiovascular diseases. The prehypertension was defined using the JNC-7 criteria. The MS was defined using NCEP guidlines. We subdivided prehypertensive patients into two groups. Group 1(306 patients) was subjects with a systolic blood pressure(SBP) 120-129mmHg or a diastolic blood pressure(DBP) 80-84mmHg. Group 2(206 patients) was subjects with a SBP 130-139mmHg or DBP 85-89mmHg. The mean age of the subjects was 59 years(range 35-80); women were 60%. The percentage of those with MS among all subjects were 19%. As expected, the percentage of MS in group 2 was significantly higher than in group 1(34.4% versus 8.8, P<0.001). Hcy concentrations ranged from 4.5-74.2umol/L(mean, 9.76). Hcy levels were significantly higher in those with MS (mean 12.5umol/l) than those without.(12.5 versus 9.76umol/L, P<0.001). Also, Hcy levels were significantly higher in group 2 than in groug 1(10.1 versus 9.5, P=0.024). The adjusted OR for raised Hcy and prehypertensive groups, comparing patients with and without the MS was 1.20 (95% CI 1.05-1.32) and 5.12 (95% CI 2-12.7), respectively. Conclusions- Higher prehypertensive group(group 2) is strong relationship with MS and Hcy levels. Also, Hcy levels were independently associated with MS in prehypertensive patients. These findings support the importance of hypertension among MS components and a clear association between Hcy levels and the MS. Key Words : Homocysteine, metabolic syndrome, prehypertension.