A case of massive cyclophosphamide hemorrhagic cystitis is presented. A 47-year-old woman with Evans syndrome was treated with a total dose of 56.6 g of cyclophosphamide for 2 years. Six months after the cessation of administration, massive hemorrhagic cystitis suddenly occurred following a common cold. Embolization of bilateral internal iliac arteries was ineffective. Therefore we performed transurethral electrocoagulation broadly for bleeding mucosa. The day after operation, bleeding from the bladder remarkably decreased and further transfusions were hardly required.