1. The case is reported of a woman in whom a macrocytic anemia developed after a short-circuit operation for regional ileitis. At a second operation, multiple constrictions and distentions were present in the bypassed loop.
2. The literature of macrocytic anemia associated with intestinal stenosis and anastomosis is reviewed. The anemia differs from Addisonian pernicious anemia in that the gastric secretion of hydrochloric acid and intrinsic factor may be normal. There need be no steatorrhea. It is concluded that the anemia is probably due to stagnation of intestinal contents and the absorption of toxic substances.
3. The production of blind loops in the small intestine of experimental animals offers a promising approach to the study of the macrocytic anemias.