The discovery of epoietin (EPO) and the cloning of its gene facilitated the understanding of the mechanism of control behind red blood cell formation. This cloning was followed by the commercial development of recombinant human EPO (rHuEPO). The use of erythropoiesis-stimulating agents (ESAs) (epoietin, ESA, EPO) is important for the treatment of anemia in patients with chronic renal failure and cancer patients with chemotherapy-induced anemia. After several years of discussions, debates and questions, ESA, intravenous iron and blood transfusions seem to have finally found their respective indications in the treatment of anemia in cancer patients receiving chemotherapy. Now, a new question arises: What is the role of ESA biosimilars?