Objective: Hypertension (HT) and prehypertension (preHT) were independent predictors of cardiovascular diseases. Urinary albumin leakage is a manifestation of generalized vascular damage. B-type natriuretic peptide (BNP) is a vasoactive peptide secreted by left ventricle in response to myocytic stretch. We aimed to investigate relationship between microalbuminuria (MA) and BNP in untreated elevated blood pressures. Methods: Of 105 untreated prehypertensive subjects (53 men, 52 women), 100 hypertensive subjects (51 men, 49 women) and 57 normotensive subjects (32 men, 25 women) none had history of diabetes. Urine albumin excretion was measured by immunoradiometric assay in morning urine sample. Results: The prevalence of MA was higher in hypertensive group than in prehypertensive group and in normotensive group (Hypertensive group; 33.9%, prehypertensive; 25.9%, normotensive; 10%). Subjects with HT had higher prevalence of microalbminuria; larger body mass index, higher levels of triglycerides, blood glucose and creatinin were more common in subjects with HT than in those with preHT. In hypertensive group; patients with microalbuminuria had higher systolic blood pressure (SBP), BNP, LVMI and lower eGFR as compared to those without MA. MA was significantly correlated with LVMI, BNP and SBP. In multivariate regression analysis, SBP (beta: 0.361; P < 0.001), LVMII (beta: 0.267; P = 0.011) and BNP (beta: 0.284; P = 0.005) were independent variables associated with MA in hypertensives. In prehypertensive group; patients with microalbuminuria had higher SBP, BNP, LVMI and lower eGFR as compared to those without MA. MA was significantly correlated with LVMI, BNP and SBP. In multivariate regression analysis, SBP (beta: 0.264; P = 0.002), LVMI (beta: 0.293; P = 0.001) and BNP (beta: 0.168; P = 0.045) were associated with MA in prehypertensives. Conclusions: In preHT and HT, SBP, BNP and LVMI are associated with MA. In the evaluation of increased blood pressures, in case of increased BNP and LVMI, MA should be investigated even in prehypertensive stages. The subjects with increased blood pressures should get medical treatment to prevent the effects on vascular structure and myocardium even in prehypertensive phase.