The nm23 gene is a potential metastasis suppressor gene originally identified using a murine melanoma cell line. The expression of nm23-H1 protein was examined immunohistochemically in 50 eligible patients with esophageal squamous cell carcinoma (ESCC). The expression was not correlated with other prognostic factors including lymph node metastases; however, overall survival rates of nm23-H1-negative patients were significantly shorter than those of nm23-H1-positive patients (P < 0.05). Furthermore, reduced expression of nm23-H1 was associated with shorter overall survival in patients with involved lymph nodes (P < 0.01), but not in patients without involved lymph nodes. These data support the conclusion that reduced expression of nm23-H1 may be associated with poor prognosis of ESCC patients, suggesting the value of nm23-H1 expression as a prognostic marker for ESCC patients, especially ESCC patients with involved lymph nodes.