Tumor-associated antigens recognized by cellular or humoral effectors of the immune system are potential targets for antigen-specific cancer immunotherapy. NY-ESO-1 is one of the most immunogenic cancer/testis (CT) antigens and emerges as the potential candidate for specific immunotherapy. We studied mRNA expression status of NY-ESO-1 in 63 cases of NSCLCs using the real-time reverse transcription PCR to examine the relationship between its expression and clinicopathological features. NY-ESO-1 expression was present in 20 (32%) of 63 NSCLC cases and significantly increased with the advancement of disease stage in TNM classification (P=0.013), especially related to lymph node metastasis (P=0.020). Moreover, frequency of NY-ESO-1 expression was related to the degree of pathological differentiation (P=0.035). The quantity of NY-ESO-1 expression by real-time RT-PCR was not correlated with any clinicopathological factor. Our results demonstrate that the NY-ESO-1 expression was frequently present in primary NSCLC, especially advanced cases with lymph node metastasis. In addition, the high incidence of NY-ESO-1 expression in NSCLC suggests the possibility of a specific immunotherapy for NSCLC.