Objective To observe the renoprotective effects of angiotensin Ⅱ (ATⅡ) receptor antagonist, L-158809 and to explore its potential mechanisms. Methods The experimental rats consisted of normal control and type 2 diabetic model groups with or without treatment of L-158809 (2 mg?kg -1 ?d -1 ) for 16 weeks. Blood glucose, HbA 1c , serum immunoreactive insulin, serum creatinine, mean arterial blood pressure, creatinine clearance (Ccr) and urinary albumin excretion index (UAEI) as well as plasma and renal ATⅡ content were measured. The kidney morphological changes were examined by renal histopathology. Marix metalloproteinase-2 (MMP-2) and the tissue inhibitor of metalloproteinase-2 (TIMP-2) expression in renal tissues were studied by immunohistochemistry, zymography and Western blot. Results In type 2 diabetic rats, L-158809 restored the blood pressure (P