To determine whether the expression level of SOX9 protein is associated with the histological characteristics of NSCLC, 142 paraffin-embedded, archived NSCLC clinical specimens, which included 32 cases of stage I, 25 cases of stage II, 58 cases of stage III, and 27 cases of stage IV lung cancers, were examined by immunohistochemical staining with an antibody against human SOX9. The gene discussed is SOX9; the disease is lung cancer.