Immunohistochemical expression of Lewisy, sialyl Lewisx, and sialyl Lewisa were examined in relation to blood vessel invasion and prognosis in 133 patients with stage I non-small cell lung cancer who had a curative resection from 1980 to 1991. Expression of sialyl Lewisx in adenocarcinomas was higher than in squamous cell and large cell carcinomas, and Lewisy immunoreactivity was the highest among the three antigens. The frequency of blood vessel invasion was significantly higher in tumors with expression of Lewisy or sialyl Lewis antigen (sialyl Lewisx or sialyl Lewisa), however, Lewisy expression was even more significant. The postoperative survival was significantly shorter when tumors expressed both the Lewisy and sialyl Lewis antigen. However, the survival of patients with either Lewisy or sialyl Lewis antigen expression was similar to that of patients whose tumors did not express either the Lewisy or sialyl Lewis antigens. These results suggest that Lewisy and sialyl Lewis antigen may be of prognostic value for metastatic potential but have different functional roles in tumor cells.