Vesicoureteral reflux during formalin therapy of intractable hemorrhagic cystitis can be prevented with Fogarty catheters inserted cystoscopically into the lower ureters. With this technique formalin instillation and cystography can be done through the cystoscope at the same time. Topical intravesical vasopressin did not, in our experience, lessen the bladder hemorrhage.