There have been concerns regarding long-term adverse effects of cyclosporine A (CSA) on renal allograft function. In a retrospective study, we compared long-term allograft function up to 70 months after renal transplantation in pediatric recipients treated with and without CSA, using iothalamate clearance to assess glomerular filtration rate. Patients received CSA, prednisone, and azathioprine (CSA group, n = 16) or prednisone and azathioprine alone (Pred/AZA, n = 11). At 48 months post transplant, the iothalamate clearances (mean +/- SD) were 57.9 +/- 26.8 ml/min per 1.73 m2 in the CSA group and 68.5 +/- 20.2 in the Pred/AZA group (P > 0.05). The mean of the slopes of individual iothalamate clearances versus time during the first 70 months following transplantation were -0.156 in the CSA group and 0.095 in the Pred/AZA group. Neither slope was statistically different from zero. These data suggest that allograft function is not significantly depressed by CSA at 48 months post transplantation and that there is no greater rate of decline in allograft function up to 70 months post transplantation in patients receiving CSA when compared with the AZA/Pred group.