The glycoprotein hormone erythropoietin is an essential viability and growth factor for the erythrocytic progenitors in the bone marrow. Tissue hypoxia is the main stimulus for the synthesis of the hormone in the kidneys and the liver. Endogenous erythropoietin and recombinant human erythropoietin (rHu-EPO) are similar with respect to their biological and chemical properties except for some microheterogeneities in their 4 carbohydrate chains. Generic products and alternatives to rHu-EPO are in development. Renal anemia can be corrected by rHu-EPO in a dose-dependent and predictable way without major side effects apart from a possible increase in arterial blood pressure. The optimal target hematocrit still needs to be defined. There are rare reports of antibody formation towards rHu-EPO in humans. Patients suffering from non-renal anemias may also benefit from the prescription of rHu-EPO. The drug has been approved for treatment of tumor patients with platinum-induced anemia. The cost-effectiveness an d medical justification of the administration of rHu-EPO in tumor patients with respect to its positive effects on tumor oxygenation, tumor growth inhibition and support of chemo- and radiotherapy is still a matter of debate. In surgical patients, the pharmacological application of rHu-EPO can increase the yield of blood units in autologous blood donation programs and lower the severity and duration of postoperative anemia, if applicated some days prior to surgery. While rHu-EPO is a godsend in medical practice, its abuse as an performance enhancing drug by athletes in endurance sports is an unethical and potentially dangerous procedure. Unequivocal methods for detection of rHu-EPO doping still need to be established.