To determine the reference intervals of urinary albumin, immunoglobulin G, transferrin, alpha 1 microglobulin, and N-acetyl-beta-D-glucosaminidase, we measured those components and creatinine in urine from men with normal blood pressure(systolic < or = 139 mmHg and diastolic < or = 89 mmHg), HbA1c < or = 5.8% and negative qualitative tests of urinary protein and hematuria. The subjects were 150 men in their thirties, 136 in their forties, and 135 in their fifties. Urines was collected in the morning after at least 12 hours fast and stored at -80 degrees C until assayed. The levels of creatinine decreased with age, whereas no change was observed in the levels of other urinary components. Consequently, the levels of those components expressed as g. creatinine increased with age. The reference intervals per g. creatinine were determined for each age-bracket using the iterative truncation method after logarithmical transformation of the values.