Introduction. Microalbuminuria(MA) or increased pulse wave velocity(PWV) have been known to be an index of subclinical target organ damage. Hypothesis. The hypothesis for this study is that microalbuminuria is independently associated with PWV in prehypertensives. Methods. MA and brachial–ankle PWV (b-aPWV) were investigated among 2263 prehypertensives (2138 men, mean age 52짹11 years) with ABI of more than 0.95. The subjects were classified into 3 groups according to UACR(urinary albumin creatinine ratio) in morning urine specimens: normoalbuminuria(<30關g/mg), microalbuminuria(30-300 ug/mg), and macroalbuminuria(>300ug/mg). B-aPWV was subdivided into 2 groups; normal group(967 subjects) is defined as subjects of 1366cm/sec or below, abnormal group(1296 subjects) as those of above 1366cm/sec. Results. The prevalence of MA in the abnormal group of b-aPWV were significantly higher than in the normal group.(7.6% vs. 4.1%, p<0.001) There were significant differences of b-aPWV values among the three groups. (normoalbuminuria, 1424짹206cm/sec: microalbuminuria, 1526짹259 cm/sec:macroalbuminuria, 1582짹212 cm/sec, p-value < 0.001). In multivariate models, the MA group significantly was associated with higher ORs for increased b-aPWV, as compared with the normoalbuminuric group.( Table 1) Conclusions. Microalbuminuria is independently associated with increased arterial stiffness in prehypertensives, suggesting that the relationship might provide more information on the assessment of subclinical target organ damage in prehypertensives.