On a consecutive series of 100 cases of gastric carcinoma, htstochemi‐cal investigation of mucous material and 7 kinds of enzymes, including dehydrogenases, phosphatases, and lysosomal enzymes was performed. Mucous membrane of twenty stomachs resected for ulcer served as control. Histologically, thirty of the carcinomas were well‐differentiated, 47 moderately differentiated, and 23 undifferentiated adenocarcinomas. A combination of histochemical reaction of two enzymes, alkaline phosphatase and aminopeptidase was found to be characteristic for the intestinal epithelium, both benign and malignant. Thus, carcinomas consisting of malignant epithelium fulfilling these characteristics could be classified as of intestinal epithelial type, and the others as of non‐intestinal epithelial type. Correlation of tubular structural differentiation of carcinoma and this histochemical differentiation was examined: 14 of 30 (46.7%) morphologically well differentiated, 20 of 47 (42.6%) moderately differentiated, and 10 of 23 (43.5%) undifferentiated adenocarcinomas were classified histochemically in the intestinal epithelial type. There is, apparently, no direct correlation between the enzymatic characteristics and the morphological tubular “differentiation”. It is apparent that the diffuse type of LAUREN16is not “non