The detection of HLA-G expression might serve as a clinical marker in the diagnosis or prediction of clinical outcomes for certain types of carcinoma. The aim of this study was to determine whether the detection of HLA-G has any important clinical applications for patients with esophageal squamous cell carcinoma (ESCC) by using immunohistochemical methods. We observed that the HLA-G protein was expressed in 90.9% (110/121) of the primary sites of ESCC but not in the normal esophageal tissues. The expression of HLA-G in the tumors was significantly correlated with histologic grade, depth of invasion, nodal status, host immune response, and clinical stage of disease. Patients with positive HLA-G expression had a significantly worse prognosis. In multivariate analysis, HLA-G was an independent prognostic factor. Our results indicate that expression of HLA-G is a characteristic feature of ESCC and suggest that immunostaining by anti-HLA-G antibodies may be a potentially useful prognostic indicator.