Abstract: Objective : To study the expression of CK1δ and COX-2 in esophageal squamous cell carcinoma and to analyze its relationship with the clinical pathological features. Methods : Immunohistochemistry (SP) was used to detect the expression of CK1δ and COX-2 in 63 specimens of esophageal squamous cell carcinoma and their adjacent mucosa. Of these 63 specimens, 30 were normal esophageal epithelium, 19 showed mild atypical hyperplasia, and 14 showed severe atypical hyperplasia. Flow cytometry (FCM) was employed to detect the expression of CK1δ and COX-2. We used SPSS11.5 to analyze the experimental data. Results : The expression of CK1δ and COX-2 was lower in normal esophageal squamous epithelial tissues than in mild atypical hyperplasia, severe atypical hyperplasia and esophageal squamous cell carcinoma (P<0.01). The expression of CK1δ and COX-2 was lower in mild atypical hyperplasia than in esophageal squamous cell carcinoma (P<0.01). No significant difference was found in CK1δ and COX-2 expression between mild atypical hyperplasia and severe atypical hyperplasia (P>0.05), and between severe atypical hyperplasia and esophageal squamous cell carcinoma (P>0.05). In esophageal squamous cell carcinoma, the CK1δ protein level was significantly higher in patients with lymphatic metastasis than in patients without lymphatic metastasis (P<0.01). CK1 δ protein expression was not related to the histological differentiation or the depth of infiltration (P>0.05). The COX-2 protein level was significantly higher in patients with lymphatic metastasis than in patients without lymphatic metastasis (P<0.01). The COX-2 protein level was higher in the cases with fibromembranous infiltration than in the cases without fibromembranous infiltration (P<0.01). COX-2 protein expression was not related to histological differentiation (P>0.05). There was a significant positive correlation between CK1δ expression and COX-2 expression (r =0.482, P<0.01). Conclusion : The abnormal expression of CK1δ and COX-2 may be involved in the oncogenesis and metastasis of esophageal cancer. Detecting these two protein levels provides information for evaluating malignancy and judging the metastatic potential of esophageal squamous cell carcinoma.