A number of conditions can contribute to the development of the anemia that inevitably occurs with end-stage renal disease. The primary ones are decreased production of erythropoietin (EPO), decreased response to EPO by the bone marrow, and shortened red cell survival. Dialysis improves hematocrit levels by reducing plasma volume and by increasing red cell mass as a result of clearing some of the middle molecule uremic toxins that affect EPO efficiency and red cell survival time. Patients undergoing continuous ambulatory peritoneal dialysis generally show higher hematocrits and lower transfusion dependencies than hemodialysis patients. The development of recombinant human EPO (EPOGEN, AMGEN Inc, Thousand Oaks, CA) largely ends the transfusion dependence of hemodialysis patients and may prove efficacious in those patients who are not transfusion dependent but whose low hematocrit levels may cause debilitating symptoms.