To explore the possibility of using tumor antigen encoded by MAGE-3 gene as the target for immunotherapy for non-small cell lung cancer (NSCLC) patients, the expression of MAGE-3 mRNA in 3 human lung cancer cell lines and 56 NSCLC samples together with the adjacent normal lung samples was determined by RT-PCR. The results showed that all 3 human lung cancer cell lines expressed MAGE-3 mRNA; of the 56 NSCLC samples, 30 expressed MAGE-3 mRNA. The expression rate in squamous cell carcinoma was significantly higher than in adenocarcinoma, whereas none of the adjacent normal lung samples expressed MAGE-3 mRNA. This study suggests that MAGE-3 mRNA is expressed in a high percentage in NSCLC specimens, and its encoding tumor antigen may be the target for immunotherapy for NSCLC patients.