Abstract: Objective To study the expression of transforming growth factor-β₁ in kidney in SHR and its role in renal fibrosis and the effects of perindopril on the renal fibrosis. Methods Seventeen SHR of nine weeks of age were randomly assigned to control SHR（vehicle once daily,n =10）or T-SHR（perindopril,4mg·kg -1 ·d -1 ,PO,n =7）. WKY（ n =7） rats were used as control. After ten weeks,the serum concentration of TGF-β₁was examed by ELISA. Immunohistochemistry was applied to measured collagen Ⅰ,Ⅲ and TGF-β₁ in the renal interstitium;expression of TGF-β₁ mRNA in the kidney was analyzed by RT-PCR. Results In SHR,kidney weight/body weight（KW/BW）increased significantly. KW/BW was significantly decreased by perindopril. There were no significant difference in serum TGF-β₁ levels among the three groups（ P ＞0.05）. Immunohistochemistry studies revealed significant interstitial accumulation of collagens Ⅰ,Ⅲ and TGF-β₁ in SHR as compared with those of WKY rat （ P ＜0.01 or P ＜0.05）. These changes in SHR were significantly attenuated by perindopril. Farther-more,perindopril substantially lower the over-expression of TGF-β₁ mRNA of SHR（ P ＜0.01）. The expression of collagens Ⅰ,Ⅲ in renal interstitum was correlated with the accumulation of TGF-β₁ in renal（ P ＜0.01）,while not related with the serum concentration of TGF-β₁（ P ＞0.05）. Conclusion The renal tubulointerstitial fibrosis of SHR was most likely mediated by an increased level of TGF-β₁ in renal tissue. Perindopril decrease the expression of TGF-β₁ ameliorate tubulointerstitial fibrosis.