Twenty-fine samples of stomach and 25 samples of adenocarcinoma stomach were employed for this study. The former have been collected from the patients of duodenal ulcer. Specimens were taken from the large curvature and pylorus. In the adenocarcinoma of stomach, materials were taken from the cancer focus and the cancer margins, fixed in 10% formalin-GaCl_2 Solution, embedded in paraffin and cut at 5? in thickness. Then they were examined with defferent reactions of histochemistry; PAS, Alcian blue (AB), Toludine blue (TB) and Barnett's method. The surface of gastric mucosa obtained from patients of duodenal ulcer after subtotalgastrectomy was covered with a substance which consists of neutral and acid mucopolysaccharide and protein. The epithelial cells of the mucosa contains large amount of neutral muco-polysaccharide. The cells of the neck of gastric gland contain quite a bit of acid muco-polysaccharide, but the cells of the deep segments of the glands do not show any of it. The cells of adenocarcinoma of stomach contain a different deal material mixture which consists of acid muco-polusaccharide and protein. The surface of the cavity in the well-differenlialed cancer glands was covered by a positive substance in TB, AB method, which forms a thin layer of membrance. An evenly distributed substance in the cavity of carcinoma gland was shown with positive reactions of PAS, AB, TB and protein. The degenerated cells show a positive reactions of PAS and protein. The cells of low-differentiated cancer were surrounded with a superficial layer of the acid mucopolysaccharide. The interstitia in the invaded margines often showed clear, distinct positive PAS and TB reactions. It indicates that it cortains more chondroitin sulfuric acid and the hyaline acid. In the superficial layers of mucosa of the cancer tissue, the epithelial cellswere often to have less positive substance than that of the membrane in the parts of cancer margine, it means a lesser amount of neutral-polysaccharide. But the acid muco-polysaccharide in the surface of cancer and its metaplastic margin clearly increases in amount than the metaplastic area far away from the cancer focus. This report discussed the significance of the increased muco-polysaccharide in the tissue of the gastric cancer.