Background: The main goal of this study was to evaluate the diagnostic efficacy of reverse transcription-nested polymerase chain reaction (RT-nested PCR) in bronchial washing fluid with MAGE A1-6 common primers for the detection of lung cancers invisible by bronchoscopy. Methods: To determine the expression of MAGE A1-6 gene in 189 lung cancers diagnosed by conventional fluoroscopy-guided lung biopsy and 89 cancer-free controls, RT-nested PCR was performed in bronchial washing specimens. We analyzed MAGE A1-6 RT-nested PCR data according to tumor histology, stage, size, and compared them with cytological data. Results: 189 patients (111 cases in adenocarcinoma, 47 cases in squamous cell carcinoma, 22 cases in small cell lung carcinoma, and 9 cases in other cancers) and 89 benign patients were investigated. The expression of MAGE was performed by nested RT-PCR using common MAGE primer. Among 189 cancer patients, the expression rate of MAGE was 49.2%, and the positive predictive value was 89.4%. However, the expression rate of MAGE in patients with benign lesions was 12.4%. In peripheral lung cancer, the positive rate of MAGE expression was 57.4% in squamous cell carcinoma, 44.1% in adenocarcinoma and 59.1% in small cell lung cancer. Whereas the expression rate of bronchial washing cytology in peripheral lung cancer was 9.0% (p=0.011). Conclusion: MAGE RT-PCR in bronchial washing fluid gave us promising data for the detection of peripheral lung cancer. It could be a useful method for selecting diagnostic tools for peripheral lesions.