Serum metalloproteinase matrix (M MP )-9, tissue inhibitor of metalloproteinase (TIMP)-1 and type Ⅳ collagen level s were measured in patients with diabetic nephropathy (DN). The severity of DN w as determined by urinary albumin excretion rate. The results show that signific ant increases of serum TIMP-1 and type Ⅳ collagen depend on severity of DN, wh ile MMP-9 tends to decline. TIMP-1 and MMP-9 seem to participate in the patha genesis of DN.