Cyclophosphamide is a well established cytotoxic drug used in the treatment of lymphoproliferative disorders, certain solid tumors, and nonneoplastic disorders such as the nephrotic syndrome, systemic lupus erythematosus, and rheumatoid arthritis. Hemorrhagic cystitis can be a complication of this drug in from 2% to 40% of patients so treated. At times, the hemorrhage may be severe, protracted, and life-threatening. Cyclophosphamide therapy has also been implicated as the causative agent in 32 cases of carcinoma of the bladder and three cases of carcinoma of the renal pelvis.