Abstract: Objective :To study the relationship between the expressions of p65 proteins of nuclear transcription factor kappa B(NF-KB)and its suppressor protein-IKBcxand the infiltration and metastasis of esophageal squamous cell carcinoma. Methods :S-P immunohistochemical method was used to detect the expressions of p65 proteins of NF-KB and IKBcx protein in the specimens of 61 cases with esophageal squamous cell carcinoma. Results :There was no correlationship between the positive expression of p65, IKBcx protein in plasma and the tumour grade, depth of infiltration and lymphatic metastasis of esophageal squamous cell carcinoma, but there was a positive correlationship between the positive rate of p65 expression in nuclei and the tumour grade, depth of infiltration and lymphatic metastasis of esophageal squamous cell carcinoma(P<0.01)and between the positive rate(KBcx protein expression in nuclei and the lymphatic metastasis of esophageal squamous cell carcinoma(P<0.05). In the esophageal squamous cell carcinoma, the positive rates of IKBcx protein in plasma and nuclei were both higher than that of p65 protein, but there was no significant difference and correlationship between them. Conclusions :Conclusion: The expression of p65 proteins of NF-KB in nuclei may be correlated with tumour grade, infiltration and lymphatic metastasis of esophageal squamous cell carcinoma. The expressign of KBcxproteins in nuclei may be correlated with the lymphatic metastasis of esophageal squamous cell carcinoma.