A case of probable hypersensitivity reaction with multi-organic failure, following bladder installation of BCG, in a male with a diagnosis of bladder carcinoma is presented. The patient developed respiratory, renal and liver failure as well as leukocytosis, thrombopenia and an increase in muscular enzymes. It was resolved with hemodynamic support. The rare complication, occasionally described in medical literature and its probable pathogenic mechanisms are discussed.