Six patients with myelodysplastic syndromes (MDS) and two patients with chronic lymphocytic leukemia, all with severe anemia entered the study. Before treatment reasons of secondary anemia were excluded. Concentration of erythropoietin, iron, transferrin, ferritin were measured before, and in the second and the third month of the trial. A r-HuEpo dosage of 80 U/kg was administered intravenously three times weekly for a minimum of three months. Four patients finished the study. The increase in hemoglobin concentration by 6 g% was observed in one patient with MDS subtype RA. In three other patients who apart from r-HuEpo received chemotherapy transfusion requirements decreased by 90%. Together with increase in hemoglobin decrease in ferritin was observed. The correlation between r-HuEpo and endogenous erythropoietin and ferritin was defined.