In summary, the anemia of CRF results from several interactive processes, chief among these inadequate Ep production relative to the degree of anemia. The anemia of renal failure can be regarded as an endocrine deficiency state, which is corrected by the specific replacement therapy. The advances of molecular biology have provided a biosynthetic Ep, a potent tool for correction and prevention of the anemia of renal failure. However, new problems often arise as new treatments become available. The rapid improvement in hematocrit and the resultant lowering in plasma volume may affect dialysis clearances in hemodialysis patients. Since the well-being and appetite of the patients improves as the hematocrit rises, newer methods to increase the weekly dialysis clearances will be needed to prevent the complication of underdialysis in these patients.