The purpose of this experimental study is to determine whether children can safely be withdrawn from Prograf® after transplantation and changed to Rapamycin® (sirolimus). Recent research studies in adult transplantation have demonstrated that with the use of Rapamycin® (sirolimus), it is possible to discontinue the use of Prograf (tacrolimus) with no increase in rejection, with decreased scarring in the kidney, and with improvements in kidney function and survival of the kidney. A total of 50 children will enroll in this study at university centers around the country. This study will last about 3 years.