BACKGROUND: The most impotrant prognostic factor is TNM stage in non-small cell lung cancer. (The most important prognostic factor in non-small cell lung cancer is the TNM stage.)Even after complete resection in early non-small cell lung cancer, (the)five-year survival (rate)is still low.Then,new prognostic factors including molecular biologic factors are found to guide the treatment of patients with non-small cell lung cancer.(However,new prognostic factors, including molecular biologic actors, have recently been found to guide the treatment of patients with non-small cell lung cancer.) We evaluated the prognostic value of (the)loss of blood-group antigen A in tumor tissue,which has been implicated (as)an important prognostic factor for overall survival and the time to progression of disease (timing of the diseaseprogression). METHODS: The loss of blood-group antigen A was assessed immunohistochemically in paraffin-embedded tumor samples from 26 patients with blood type(s)A or AB,who underwent (had undergone) curative surgery.Monoclonal antibody was used to detect the blood group antigen A expression. RESULTS: 15 (Fifteen)patients (58%)expressed antigen A in their tumor tissue,whereas 11 patients()(42%)didn't (did not) show antigen A. Median survival time of blood A antigen positive group was 11 months, but that of blood A antigen negative group was 18 months. The survival difference between both group couldn't reach the statistic significance. (The median survival time of the blood A antigen positive group was 11 months,while the median survival time of the blood A antigen negative group was 18 months.The difference in survival between the two groups was not statistically significant.) CONCLUSION: Loss (The loss)of blood-group antigen A in tumor tissue couldn't (was not found to)be a significant prognostic factor in patients with non-small cell lung cancer.This study needs to be extended for further evaluation.