Abstract: Objective To study changes PCNA in radiotherapy of esophageal carcinoma and analyse the validity of PCNA expression on prognosis. Methods From Nov.1979 to Dec.1996,91 patients were treated by preoperative radiotherapy plus radical esophagectomy in our hospital.All were confirm as squamous cell carcinoma.Two vertical irradiation fields to deliver a dose of 30～40GY/15～20F/3～4W and PCNA with immunohistochemical staining. Results The overexpression rates wree 71 4% and 57 1% for the post and pre radiotherapy, P =0.04.The survival rate of overexpression were lower than those lowexpression in post radiation, P =0.0001.The various changes of PCNA between pre and post radiation,show different survival rates, P =0.00001.The survival time differed with different reduction of PCNA indexes. Conclusion ① PCNA protein expression rise after pre operative radiotherapy of esophageal carcinoma,may signify the repopulation of tumor cells.② The survival periods were poor for patients with overexpression and the prognosis was good for patients who show a conspicuous reduction of PCNA index after radiotherapy.