Familial juvenile nephronophthisis (FJN) is a hereditary renal disease, characterized by a juvenile onset and the development of medullary cysts and progressive renal damage. The pathogenesis of FJN remains unknown, and at present, no rational therapy other than renal transplantation is available. We describe two cases in siblings in whom there were no extrarenal complications, such as retinopathy or central nervous system involvement. Both patients display juvenile onset of the disease and end-stage renal failure. The brother received a kidney from his father, and the sister received a kidney from her mother. Recurrence of the underlying disease has not so far been found in the transplanted kidney.