Idiopathic membranous nephropathy is a well recognized cause of nephrotic syndrome. The disease is more common in adults than children and in men than women. The clinical course is variable, and some patients will be treated by renal transplantation. The clinical course, however, of such patients after transplantation has yet to be thoroughly documented. This report describes a man of 47 with membranous nephropathy, who developed chronic renal failure. He received a cadaver renal allograft. Two months later, massive, persistent, proteinuria developed. A biopsy specimen of the allograft showed changes characteristic of membranous nephropathy and identical to those present in the patient's own kidney. The criteria for recurrence of glomerulonephritis in renal allografts are met in this case.