A 49-year man, with past history of right total nephroureterectomy due to urothelial carcinoma of the right renal pelvis in September 2006 and left partial ureterectomy due to contralateral ureteral recurrence in October 2007, underwent TUR-BT due to superficial high-grade recurrent bladder cancer. After TUR-Bt, he was treated with intravesical Bacillus Calmette-Guérin (BCG) instillation at weekly intervals. Just after 5th instillation, he suffered a continuous high fever up to 38 degrees C and complained of general fatigue. Chest CT showed diffuse micronodular shadows in both lungs, and serum liver enzyme was markedly elevated. All cultures from his sputum and urine were negative for mycobacterium tuberculosis. TB-PCR test and quantiferon were also negative. These findings together with no improvement of the symptoms with anti-tuberculous treatment finally made us to judge that this was due to a hypersensitivity reaction to BCG. Soon after pulse steroid therapy, body temperature was normalized and the abnormal findings of the lung and liver disappeared.