This study was conducted to clarify the relationship between E-cadherin expression on tumor and lymph node metastasis as well as its prognostic roles in resected non-small-cell lung cancer. Two hundred forty-nine patients, who underwent surgical resection (stage I-IIIA), were examined. Paraffin-embedded sections of the primary tumors in all cases and of the metastatic lymph nodes in stage IIIA disease were stained with a monoclonal antibody against E-cadherin. Decreased expression of E-cadherin correlated with pathologic stage, tumor size, lymph node metastasis, and histological grade. The 5-year survival rate of E-cadherin-negative patients with stage IIIA disease was significantly lower than that of E-cadherin-positive patients. Multivariate analysis in stage IIIA disease indicated that E-cadherin was an independent prognostic factor. In the patients with clinical N0 tumors, the frequency of pathological N2 tumors was significantly higher in cases where the primary tumor was recognized as E-cadherin expression negative than in cases where the primary tumor was recognized as positive. Decreased E-cadherin expression showed correlation with presence of lymph node metastasis in resected non-small-cell lung cancer and with the prognosis of patients with stage IIIA disease.