The Mitomycin C is a chemotherapeutic agent used in several types of carcinomas. In the superficial vesical carcinoma comes using since more than a quarter century in the form of endovesical instillations. It is a drug relatively safe, although there have been described adverse effects related to its systemic administration as myelosuppression, anaemia, kidney toxicity and less frequently pulmonary fibrosis. In this article we presented the case of a patient who suffers a respiratory illness compatible with interstitial lung disease that develops a respiratory severe insufficiency finishing with the death, after the administration of endovesical mitomycin C, being this adverse effect exceptional for this route of administration.