To investigate the expressions of transforming growth factor (TGF)-beta1 and collagen IV in the renal tissues of patients with chronic allograft nephropathy (CAN).Immunohistochemical method and computer-assisted image analysis system were used to detect the expressions of TGF-beta1 and collagen IV in the renal tissues of patients with CAN, and the association between TGF-beta1 and collagen IV expressions as well as that between their expressions and the pathological grading of CAN were analyzed.The expressions of TGF-beta1 and collagen IV were significantly higher in the renal tissues of the patients than in normal renal tissues (P0.001), and the expressions tended to increase with the pathological grades of CAN; TGF-beta1 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, P0.001; r=0.910, P0.001).Abnormal collagen IV deposition is one of the major factors associated with renal fibrosis in CAN, and TGF-beta1 might play an important role in renal fibrosis in CAN through up-regulation of collagen IV in the renal tissues.