Long-term kidney allograft survival continues to remain an elusive goal. Kidney transplant recipients are believed to be at high risk for loss of allograft function, and new, potentially non-nephrotoxic immunosuppressive medications are advocated to improve long-term allograft survival. To evaluate the efficacy of such therapeutic interventions, information regarding the change in GFR among kidney transplant recipients with long-term allograft survival is needed. We studied 40,963 transplant recipients between 1987 and 1996 with allograft survival of at least 2 yr in the United States Renal Data System. Linear regression methods were applied to serial GFR estimates after transplantation. The baseline mean GFR at 6 mo after transplantation was 49.6 +/- 15.4 ml/min per 1.73 m(2). During the mean follow-up of 5.7 +/- 2.3 yr, the mean +/- standard error of the change in GFR was -1.66 +/- 6.51 ml/min per 1.73 m(2) per year (median, -0.94 L/min per 1.73 m(2) per year). A total of 12,583 (30%) of patients had improvement in GFR, 8133 (20%) patients had no change in GFR, and 20,247 (50%) patients had decline in GFR. It is concluded that, although most patients had significant impairment of GFR at baseline, the decline in GFR was slow and many patients had either no change or improvement in GFR. Strategies to improve long-term kidney allograft survival that increase baseline allograft function may be more effective than strategies to slow the decline in GFR.