1. In individuals severely infested with Ancylostoma or Necator, it is possible to maintain the normality of blood value by the administration of a sufficient dose of an iron salt. 2. The minimum dose necessary to maintain normality of the blood in an individual weighing 45 kilograms, with 1051 helminths, was 0.2. Gm. daily of ferrous sulfate, administered in mixture with manioc flour. 3. The patient observed became clinically normal two weeks after the beginning of blood regeneration up to the end of the trial period one year later. In this period, with the various doses of iron tried, hemoglobin varied from 8.0 to 11.0 per 100 ml. of blood.