We tried do ascertain what was the real significance of blood eosinophilia in ankylostomiasis and to prove that eosinophilia is not related to toxins or poisons elaborated by these helminthes. The problem is rendered on account of knowledge of the function of the eosinophils, the interpretation we present of eosinophilia in ankylostomiasis is merely provisional. We showed that the eosinophilia verified at the beginning of the disease is induced by the migration of larvae inside the organism; still the eosinophilia observed later on is not a remote consequence of the initial one, for it is due to the action of heterologous albumins lodged in the intestine and deriving from secretions of the worms appended to the mucosa of this organ. With regard to the mechanism of this eosinophilia, we will mention that eosinophilia located in the intestine may induce a transient decrease of these cells, in the circulation, which may determine an excitation of bone marrow (just like the excitation occasioned by loss of blood in acute hemorrhages) to produce new leucocytes. By virtue of the constant helminthic secretion, this organ may be constantly stimulated by this indirect condition, which mau finally convey a persistent blood eosinophilia. On the strength of some studies presented by us and on the basis of a number of results met with in the literature, we assert the inexistence of any relationship of cause and effect between eosinophilia and the factors producing the anemic syndrome. Such is our statement because we verified the complete cure of the anemia, despite the persistence of intense peripheral eosinophilia, and moreover because the more severe the anemia is the lesser the rate of eosinophilia is in blood. Apart from this, we call attention to the fact that eosinophilia is a phenomen always present when in the in most of the organism there are heterogeneous albumins, and finally that this phenomenon can be induced by physical agents and, therefore, may appear independently of any toxin or substance acting directly upon bone marrow.