Abstract: Objective To determine the association between urine transforming growth factor β1 (TGF-β1) concentration and long-term renal allograft function. Methods Patients undergoing kidney transplantation between August 1, 1999 and June 30, 2001 and survived for one year with normal renal functions were investigated. The blood and urine TGF-β1 concentrations were tested at an interval of at least 6 months. Totally 134 patients completed the 3-year follow up investigation. Correlation between their renal functions (creatinine clearance rates) and their urine relative TGF-β1 concentrations 1 year after renal transplantation were determined. Of the 134 renal recipients, 16 were diagnosed to have chronic allograft nephropathy (CAN), and their blood and urine TGF-β1 concentrations 1 year after renal transplantation were compared with those of the recipients free of CAN. Results There was a positive correlation between long-term renal functions (loss of creatinine clearance rates) and in relative concentration of TGF-β1 urine 1 year after renal transplantation. The urine TGF-β1 concentrations of CAN and CAN-free recipients 1 year after transplantation were 182.7±40.2 and 398±33.5 pg/mg·Cr, respectively, showing significant differences. The blood TGF-β1 concentrations of CAN and CAN-free recipients were comparable (32.1±4.7 and 31.9±4.8 ng/ml, respectively). Conclusion Urine TGF-β1 is significantly elevated even before the onset of renal dysfunction in patients with CAN, and urine TGF-β1 level in early stage after renal transplantation can help predict long-term renal function.