Abstract: This paper presents a quantitative study of macrophage infiltration in the stroma of 27 cases of esophageal squamous cell carcinoma using ABC method with monoclonal antibody against macrophage. Our study revealed:. Macrophage infiltrates mostly at the peripheral portion of cancer stroma, and often mixed with lymphoid cells. The deeper invasion, milder degenorative change inperipheral portion of cancer and with positive lymphnode metastasis, the weaker macrophage infil-tration appears in the stroma around the carcinoma. These data suggested that the macrophage infil-tration is an important expression of host immunologic defense against cancer.