Abstract: Objective:To investigate the expression of carbonic anhydrase Ⅸ(CAⅨ) in esophageal squamous cell carcinoma and its relationship with clinicopathological parameters.Methods:The expression of CAⅨ in 30 cases of normal esophageal tissues and 76 cases of esophageal squamous cell carcinoma tissues were detected by immunohistochemical staining,the relationships between CAⅨ expression and esophageal squamous cell carcinoma was evaluated.Results:The expression rate of CAⅨ in normal esophageal tissues(6.67%) was significantly lower than that in esophageal squamous cell carcinoma(72.06%)(P0.01).The expression of CAⅨ was significantly associated with the clinical stage,cell differentiation degree and lymph node metastasis of esophageal squamous cell carcinoma(P0.05).Conclusions:The high expression of CAⅨ is an important index in the estimation of esophageal squamous cell carcinoma prognosis.