Objective To research the effects of bosentan in on unilateral ureteral obstruction (UUO) rats. Methods Wistar rats were randomly divided into three groups. UUO group was subjected to complete ligation of left ureter, sham operation group with sham operation was used as control. Bosenten group was subjected to complete ligation of left ureter and to stomach with bosentan suspension. Three groups were killed at 5,10,15,20 d. We examined renal pathological changes and the expressions of transforming growth factor-?1 (TGF-?1) in kidney of all rats using immunohistochemistry analisis method. The plasma and ureteral obstructive kidney urinary concentration of endothelin - 1 (ET - 1) was determined by radioimmunoassay. Results In Bos and UUO groups, the urinary concentration of ET - 1 increased substantially and the expression of TGF - ?1 were much higher than those in the S group. At the same time.tubulointerstitial fibrosis was present in the kidney of rats in Bos and UUO group. But the expression of TGF- ?1 and tubu-lointerstitial fibrosis in Bos group were lower than those of UUO group. Conclusion Bosentan can effectively amelirate tubulointerstitial fibrosis in rats with UUO by ET and TGF - ?1 machanism.