The effectivity of water extract from the style of Zea mays on diabetic nephropathy was investigated in the development of new natural medicinal resources. Streptozotocin (STZ) induced diabetic rats were used to evaluate the therapeutic effect of the style. Urinary albumin excretion and creatinine clearance were examined for diagnosis of diabetic nephropathy. From these results it was learned that the style of Z. mays prevented glomerular hyperfiltration. The present findings indicated that the water extract of the title material suppressed the progression of diabetic glomerular sclerosis in STZ-induced diabetic rat.