Two patients with Ph + CML underwent URD-BMT after conditioning with Bu-Cy-LPAM. They developed hemorrhagic cystitis with an extremely complicated and painful course, caused by ureteral obstruction, requiring prolonged hospitalization. No virus other than cytomegalovirus was found and in both cases was attributed to Cy use. Treatment is usually conservative, but in the case of severe obstruction, a surgical approach should be considered and performed as early as possible to preserve renal function.