SUMMARY. A rare case is presented of granulomatous pneumonitis following intravesical instillation of Bacillus Calmette-Guerin (BCG) for the treatment of superficial urothelial carcinoma. The patient, a 59 year-old man, was admitted to hospital because of malaise, fever (39o C), dyspneoa (III/IV) and respiratory failure. He had a history of urinary bladder carcinoma treated by transurethral resection, followed by repeated instillations of BCG, a live attenuated strain of Mycobacterium Bovis, every 4 months, as immunotherapy. After the 4th instillation the patient progressively developed the symptoms that led to his admission. Physical examination revealed inspiratory crackles in both lung fields. Radiological examination with X-ray and HRCT showed bilateral patchy alveolar infiltrations, a ‘ground glass’ appearance of the lungs and multiple pulmonary nodules in the middle and lower lung zones. Laboratory examination excluded other causes of granulomatous diseases. The administration of antituberculous treatment and corticosteroids resulted in rapid clinical and radiological improvement. Pneumon 2007; 20(4):401–405