The cells which produced erythropoietin (EPO) in kidney is called renal EPOproducing cells (REPs). Insufficient production of EPO can cause renal anemia and anemia associated with chronic disease disorders. REPs transformed into scarforming myofibroblasts, resulting in renal fibrosis, chronic kidney disease (CKD) patients the EPOproducing ability of myofibroblasttransformed REPs (MFREPs) is decreased. Recently studies on REPs made great progress and the research is expected to become the treatment of renal anemia and renal interstitial fibrosis new target.