The concentrations of three trace elements (iron, copper and zinc) involved in hematopoiesis were studied in 200 patients with iron-deficit anemia, hemolytic anemia and Biermer's anemia, in comparison with a group of normal subjects. The method used was atomic absorption spectrophotometry. The results obtained showed that in iron-deficit anemia resistant to iron therapy the copper and ceruloplasmin serum concentrations are at the lowest limit of normal. This copper deficit has a negative effect on the disease by preventing hemoglobin synthesis. In iron-deficit anemias responding to iron therapy the relatively low (about 90 gamma %) zinc values have a negative effect by blocking the iron in the iron reserve. In hemolytic anemia the very high zinc serum concentrations (over 200 gamma %) may lead to a shortening of the erythrocytes life span due to its "entatic state". In Biermer's anemia zinc by its high concentration has a positive role owing to carbonic anhydrase which eliminates more rapidly carbon dioxide from the organism.