Background: Melanoma antigen genes (MAGE) are expressed in many human malignant cells and are silent in normal tissues other than in testis and in placenta. But MAGE expression in benign lung diseases, such as pulmonary tuberculosis or cases with severe inflammation, needs further evaluation to overcome false-positive findings. We evaluated detection rates of the melanoma antigen genes (MAGE) RT-nested PCR in bronchoscopic washing samples from patients with benign lung disease, as well as in patients with malignancies. Methods: Bronchial washing fluid from 122 patients was used for cytological examination and MAGE gene detection using RT-nested-PCR of common A1-6 mRNA. We compared the results from the RT-nested PCR and the pathologic or bacteriologic diagnosis. We also analyzed the expression rate and false positive rate of MAGE gene. Results: Among 122 subjects, lung cancer was diagnosed in 23 patients and benign lung disease was diagnosed in 99 patients. In patients with lung cancer, the positive rate of MAGE expression was 47.8% (11/23) and in benign lung disease group, the expression rate was 14.1% (14/99). Among benign lung disease group, the expression rate of MAGE gene (25.0%) in patients with pulmonary tuberculosis (11/44) was especially high. Conclusion: MAGE A1-6 RT-nested PCR of bronchial washing fluid can be used as a complementary method in lung cancer, but that test results in a high false positive rate in tuberculosis patients.