To investigate the relationship between microalbuminuria and hypertension in nondiabetic subjects, we selected 245 Japanese men aged 35 to 69 years on the basis of the results of a 75 g oral glucose tolerance test. Prevalence of hypertension (blood pressure levels > or =140/90 mm Hg or treatment of hypertension) in microalbuminuria-positive (0.03 to 0.3 g/d) subjects was significantly higher than that in microalbuminuria-negative (<0.03 g/day) subjects. Also, the significant increase of levels of triglycerides, serum uric acid, and area of plasma insulin were recognized in microalbuminuria-positive subjects. Urinary albumin was significantly related to both systolic and diastolic blood pressure in a manner independent of these relevant factors, including area of insulin. With regard to renal functions, creatinine clearance of microalbuminuria positive subjects was significantly increased and fractional excretion of sodium of microalbuminuria-positive subjects was significantly decreased as compared with those of microalbuminuria-negative subjects. In normotensive subjects, serum uric acid, which is known to be related to sodium handling at renal tubules of microalbuminuria-positive subjects, was significantly higher than those of microalbuminuria negative subjects as well as triglycerides and area of insulin, without the differences of the levels of blood pressure and BMI. Therefore, it is suspected that microalbuminuria is a renal facet of insulin resistance, and a predictor value of hypertension.