Recently the presence of estrogen receptor(ER) has been demonstrated in some cases of cancer of the digestive tract such as stomach, large intestine, pancreas and the liver which are non-target organs of sex hormones. The authors studied ER in tumors from 95 gastric adenocarcinomas using immunohisto- chemical staining with monoclonal antibody. DNA ploidy using flow cytometry was also as- sessed in 75 cases of gastric carcinomas. ER positivity was 40 of 95(42.1%) gastric carcinomas. The tendency of receptor positivity increased with progression of tumor and lower differentiation. There was no positive relationship between ER positivity and sex, age, gross type, DNA ploidy and the level of carcinoem- bryonic antigen. The results of this study show that hormonal factors are involved in gastric carcinomas and that the cancers have endocrinic characteristics. The sturdies clarifying the rofe of hormones to cancer cells will be valuable in the design of hormonal therapy.