The data presented in the first paper demonstrated that patients with gastric cancer suffered from a significant decrease in plasma proteins concentration on admission to the hospital, but that the postoperative course was frequently associated with a increased plasma protein content. It is the purpose of this paper to discuss these findings by the determination of plasma protein fractions. The pre- and post-operative concentrations of plasma protein protein fractions in 47 patients with gastric cancer were measured by refractometry and electrophoresis. As control material 15 normal individuals including mild patients near normal, 13 cases of rectal cancer, 13 cases of various types of cancer other than that of the alimentary tract, 9 cases of sarcoma and 29 patients with gastroduodenal ulcer-a total of 90 cases-were selected. The following results were obtained: 1. Patients with gastric cancer showed a marked decrease of albumin fraction. This is the cause of the hypoproteinemia in these patients. 2. The decreased albumin concentration in patients with gastric cancr was noted to become more profound with the progress of the disease. 3. The reduction of albumin content in patients with gastric cancer was more pronounced in the cases where the passageway of the stomach was not patent than in those where it was patent. 4. In patients with gastric cancer an increase of both globulin and fibrinogen fraction was demonstrated. 5. With the occurrence of metastasis of gastric cancer in the liver, there was found an increase in β- and γ-globulins. 6. Albumin-globulin ratio in patients with gastric cancer was lowered and became lower with the progress of the disease. 7. The albumin level and the albumin-globulin ratio in patients with gastric cancer proved to be the index of the prognosis, and albumin levels below 2.70g/dl and albumin-globnlin ratio under 1.0 were associated with an increased incidence of the cases where radical operation was not indicated and of postoperative complications. 8. The determination of plasma protein fractions was of little significance in the differential diagnosis between gastric cancer and gastroduodenal ulcer. 9. The albumin concentrations in patients with gastric cancer decreased after gastric resection. The degree of the decrease was more profound in the cases where preoperative levels of albumin were higher. On discharge from the hospital the albumin contents were, in most cases, found to increase over those before operation. 10. An increase in both fibrinogen and globulin fractions occurred after gastric resection for cancer. On discharge from the hospital these levels, although lowered, yet remained slightly higher than those before operation.