Abstract: Objective To investigate the expressions of transforming growth factor (TGF)-β₁ and collagen Ⅳ in the renal tissues of patients with chronic allograft nephropathy (CAN).Methods Immunohistochemical method and computer-assisted image analysis system were used to detect the expressions of TGF-β₁ and collagen Ⅳ in the renal tissues of patients with CAN, and the association between TGF-β₁ and collagen Ⅳexpressions as well as that between their expressions and the pathological grading of CAN were analyzed.Results The expressions of TGF-β₁ and collagen Ⅳ were significantly higher in the renal tissues of the patients than in normal renal tissues (P<0.001), and the expressions tended to increase with the pathological grades of CAN; TGF-β₁ and collagen Ⅳ expressions in both the renal glomeruli and the tubulointerstitium were in patients with CAN positively correlated with normal renal tissues (r=0.943, P<0.001; r=0.910, P<0.001).Conclusions Abnormal collagen Ⅳ deposition is one of the major factors associated with renal fibrosis in CAN, and TGF-β₁ might play an important role in renal fibrosis in CAN through up-regulation of collagen Ⅳ in the renal tissues.