Cases of gastric cancer were classified into two types, i.e. the localized and infiltrating ones. Specimens were taken from the cancer and the neighbouring part of it on sides of the greater and the lesser curvatures, and tissue respiration, aerobic and anaerobic glycolysis were investigated with Warburg apparatus. 1) The cancer tissue has decreased tissue respiration and increesed aerobic as well as anaerobic glycolysis compared with the non-cancerous tissue. Neighbouring tissue of the cancer has more similar nature to the cancer than the non-cancerous case. 2) In non-cancerous tissues, there are observed decreased tissue respiration and increased aerobic glycolysis on the side of the lesser curvature compared with the greater. 3) Neighbouring tissue of the cancer has increased aerobic glycolysis on the side of the lesser curvature. 4) In the cancer tissue, both localized and infiltrating types have decreased tissue respiration on the side of the lesser curvatrue. The infiltrating type shows increased aerobic and anaerobic glycolysis on the side of the lesser curvature, while the localized type shows no difference. 5) From these results, it is proved that the cancer tissue has more malignant biochemical nature on the side of the lesser curvature than that of the greater.