Four renal isografts have been performed and all have had satisfactory function for 7 1/2 to 17 2/3 years without prophylactic or therapeutic immunosuppression. Three of these patients originally had glomerulonephritis, and in one there was histologic evidence of recurrent disease, 7 1/2 years after transplantation, without proteinura and without change in renal function. Although this experience is small, it suggests that prophylactic immunosuppression is not appropriate for recipients of renal isografts.