Immunohistochemical expression of Lewis(y), sialyl Lewis(x), and sialyl Lewis(a) 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 Lewis(x) in adenocarcinomas was higher than in squamous cell and large cell carcinomas, and Lewis(y) immunoreactivity was the highest among the three antigens. The frequency of blood vessel invasion was significantly higher in tumors with expression of Lewis(y) or sialyl Lewis antigen (sialyl Lewis(y) or sialyl Lewis(a)), however, Lewis(y) expression was even more significant. The postoperative survival was significantly shorter when tumors expressed both the Lewis(y) and sialyl Lewis antigen. However, the survival of patients with either Lewis(y) or sialyl Lewis antigen expression was similar to that of patients whose tumors did not express either the Lewis(y) or sialyl Lewis antigens. These results suggest that Lewis(y) and sialyl Lewis antigen may be of prognostic value for metastatic potential but have different functional roles in tumor cells.