A total of 164 gastric carcinomas comprising 97 advanced cancers and 67 early cancers were examined immunohistochemically for human chorionic gonadotropin (hCG). Tumor cells containing immunoreactive hCG was found in 7 cases or 10.4% of the early cancer cases and in 11 cases or 11.3% of the advanced cancer cases. Moreover, the incidence of hCG-beta subunit positive cells was 8.2% in the advanced cancer cases and 6.0% in the early cancer cases. The incidence of these cells did not differ significantly by histological type and by infiltrative growth of gastric carcinoma. However, hCG-containing tumor cells were frequently detected in poorly differentiated or undifferentiated area within the tumor. In addition, these cells did not contain mucin or argyrophil granules. The three year survival rates indicated a tendency for advanced gastric cancer containing hCG to have a poor prognosis.