Summary1. In a series of 659 patients followed up from one to ten years after a subtotal gastrectomy for ulcer, cancer, tumor of connective tissue or polyp, an anemia (Hb<12 g/100 ml) appeared in 17 % of the cases. The mean hemoglobin values were 14,1 g for men, 12,5 g for women, or about 2 g lower than the values observed in a normal population. The anemia was hypochromic in 15 % of the cases, megaloblastic in 2 %.2. Hypochromic anemias are due to several factors :a) The role of gastric achlorhydria is of little importance : 135 achlorhydric patients had a mean hemoglobin value of 13,1 g, 23 % were anemic; 74 chlorhydric patients had a mean hemoglobin value of 13,7 g : 14 % were anemic.b) A postoperative protein deficiency reduces simultaneously the hemoglobin and serum albumin levels. In 122 cases studied, a positive correlation was observed between hemoglobin and serum protein and albumin values.c) The preoperative hemoglobin level. Patients predisposed to anemia before gastric resection keep the same tendency after the operation.d) The postoperative hemoglobin level. Anemia is much more frequent in patients with a low postoperative hemoglobin. After subtotal gastrectomy factors a-c interfere with the normal hemoglobin synthesis. It is therefore important that all blood deficiencies occuring before and during surgery be perfectly corrected.3. The few cases (14) of megaloblastic anemia encountered in partially gastrectomized patients are not a consequence of the gastric resection. Most of them are seen in patients operated on for cancer (6 cases or 4,1 %) or polyp (7 cases or 35,0 %) : in these cases, the disease is already present before the gastrectomy. Some very rare cases (1 or 0,2 %) appear after resection for peptic ulcer; their frequency being identical to the percentages observed in a normal population, it must be concluded that their appearance is a pure coincidence.