The tumor-associated carbohydrate antigens sLe(x) and sLe(a) are known to be ligands of endothelial cell leukocyte adhesion molecule-1 (ELAM-1) and to be involved in hematogenous metastasis of human cancer cells. To determine whether expression of these carbohydrate antigens in lung cancer is associated with metastatic status, we immunohistochemically evaluated the expression of sLe(x) and sLe(a) in 52 bronchofiberscopic biopsy specimens obtained from patients with various stages of previously untreated lung cancer. The incidence of sLe(x) and sLe(a) positivity by immunostaining was 65.4 and 13.4%, respectively (P < 0.01). The incidence of sLe(x) positivity in patients with adenocarcinoma (94.7%) was significantly higher than in patients with squamous cell carcinoma (52.0%) and small cell carcinoma (28.6%) (P < 0.05). The high sLe(x) immunoreactivity correlated with metastasis to a distant organ (P < 0.05), but not with lymph node metastasis. The serum levels of these carbohydrate antigens measured by a serological assay correlated with their immunohistochemically detected expression (P < 0.01). These findings indicate that sLe(x) is expressed more frequently than sLe(a) in bronchofiberscopic biopsy specimens and plays an important role in distant metastasis in lung cancer patients.