Intravesical instillation of the bacillus Calmentte-Gu rin(BCG), an attenuated strain of Mycobacterium bovis, is an approved method for the treatment of superficial bladder cancer. Because BCG is a living organism, the potential for infection exists. BCG is generally well tolerated, with complications in less than 5% of those treated with use of current practices. The most frequent symptoms of toxicity associated with intravesical BCG immunotherapy include bladder irritation, frequency, and dysuria. Systemic reactions are less common but more serious than local side effects, and include fever, chills, malaise, rash, hepatitis, pneumonitis, arthritis and sepsis. In rare cases, BCG treatment can result in a systemic infection that requires antituberculous therapy. The pulmonary toxicity that results from intravesical BCG treatment is generally characterized by one of two types : systemic allergic reaction with pulmonary reticulonodular opacities depicted on chest radiographs with cellular findings consisting of activated lymphocytes, and actual BCG mycobacteremia with a miliary pattern depicted on chest radiographs and granuloma formation which rarely results in positive acid-fast stain or culture results. Recently we experienced two types of pulmonary complications following intravesical BCG immunotherapy in patients with superficial bladder cancer. We report two cases with a review of literatures.