Résumé : Hemorrhagic cystitis that occurs late after bone marrow transplantation (BMT) in BMT recipients is often associated with adenovirus or polyomavirus BK infections. Intravesical instillation of cidofovir in a BMT recipient with intractable hemorrhagic cystitis resulted in clinical improvement. Local cidofovir therapy for viral hemorrhagic cystitis could be an alternative to intravenous administration of cidofovir.