HEMORRHAGIC cystitis can be a life-threatening problem in patients with pelvic malignancy. Bladder lavage to remove clots, transfusions, and fulguration of identifiable bleeding sites may work in some patients. Others may respond only to urinary diversion, hypogastric artery ligation, or total cystectomy. Unfortunately, patients who are debilitated, have extensive local disease, or have had previous irradiation are poor surgical candidates. To control bladder hemorrhage in these inoperable patients, Brown first reported bladder irrigation with formaldehyde solution in 1968.1 Since then, 60 patients who have undergone this procedure have been reported. Treatment was successful in 54, and only one serious complication, papillary necrosis, has occurred. Lest this remarkable success tempt urologists to use formaldehyde solution in patients with nonterminal conditions, who might still respond to other measures, we report a case of oliguric renal failure following intravesical formaldehyde solution (3.7% formaldehyde) instillation—apparently due to irreversible damage to both ureters.