Eighty-eight cases of gastric carcinoma were tested for ectopic production of HCG with anti-HCG antibody by PAP method. Among 88 cases of gastric carcinoma, 17 cases were positive for HCG. Tumors were classified as well or moderately or poorly differentiated. In the poorly differentiated group, 53.85% of the tumors were immunopositive for HCG, and 66.67% had metastasized to lymph nodes. It is suggested that gastric carcinoma may produce HCG, and HCG-positive tumors tend to have higher malignancy and poor histological differentiation. The possible origin and histogenesis of HCG-producing tumor cells are discussed.