Human erythropoietin(EPO) is a glycoprotein that enhances red blood cell production by stimulating proliferation and differentiation of erythroid progenitor cells in the bone marrow. Patients with chronic kidney disease(CKD) suffer from anemia caused by reduced production of EPO in the kidney. Recombinant human EPO protein has been used successfully for the treatment of anemia associated with CKD. Recently, attention has been paid to the development of side effect of EPO, pure red cell aplasia(PRCA), in some patients with CKD. PRCA is a rare disorder of erythropoiesis that leads to a severe anemia due to an almost complete cessation of red blood cell production. EPO-related PRCA is caused by the production of EPO-neutralizing antibodies(Abs) that eliminate the biological activity of EPO as well as endogenous EPO in patients undergoing therapy. Since 1988, almost 200 cases worldwide have been reported with Ab-positive PRCA after receiving EPO therapeutics. The underlying mechanisms of the breaking of immune tolerance to self-EPO have been investigated. Modification of formulation, organic compounds of container closures, and route of administration has been suggested for the possible mechanism of increased immunogenicity of EPO. A number of assays have been used to detect Abs specific to EPO. These assays are generally grouped into two major categories: binding Ab assays and neutralizing Ab assays(bioassays). There are several types of binding Ab assays, including radioimmunoprecipitation assay, enzyme-linked immunosorbent assay, and the BIAcore biosensor assay. In vitro cell-based bioassays have been utilized for the detection of neutralizing Abs. Finally, the recent experience with anti-EPO Abs may have considerable implications for the future development and approval of EPO preparations. Also, considering that millions of patients are being treated with EPO, clinicians need to be aware of signs and consequences of this rare but severe clinical case.