A patient with end-stage renal failure caused by bilateral kidney stones received a kidney transplant from his identical twin. No immunosuppressive therapy was given. After a few days he developed a urinary fistula from a polar artery section, which spontaneously healed. Renal function remained subnormal, blood pressure and urinalysis were normal. After one year proteinuria appeared, and after about four years it entered a nephrotic range. Renal biopsy showed focal glomerular sclerosis (FGS). In the following years progressive renal insufficiency and arterial hypertension developed, and the patient had to be submitted to regular dialysis about 9 years after transplantation. As far as we know this is the first case of late renal failure in an isograft related to the development of de novo FGS. It is suggested that de novo FGS in this isotransplant was related to the partial loss of renal mass caused by polar necrosis, which caused glomerular hyperfiltration. Another possible contributing factor may be kidney denervation, which removes an important mechanism for adjustment of renal arterial flow.