All patients should have documented chronic renal failure (CRF) and be receiving or about to receive (within 1 month) a marketed erythropoietin product by the subcutaneous route of administration at the time of enrollment. Patients may be at any stage of CRF (Stages 1 to 5) or be receiving any treatment for CRF, including predialysis, peritoneal dialysis, or hemodialysis, but should not be receiving immunosuppressive treatment following an organ transplant.