The study was to enroll approximately 180 subjects with chronic kidney disease. Eligible subjects were those with chronic kidney disease who were receiving darbepoetin alfa every two, three, or four weeks for a period of 3 months or more and who had a stable hemoglobin (Hb) level at study entry of 12 g/dL (plus or minus 1 g/dL (11-13 g/dL). Subjects receiving darbepoetin alfa every 2, 3 or 4 weeks were switched over to epoetin alfa which they received at the same dosing frequency ( every 2, 3 or 4 weeks) upon study entry and throughout the 24 week study period. Clinical safety was assessed for the occurrence and severity of adverse events. Blood tests (Complete Blood Count, platelets, reticulocyte count, iron, were assessed at pre-determined intervals throughout the study. Vital signs (e.g. Blood pressure) were checked at each visit. Subjects received epoetin alfa at the same dosing frequency that they had previously received darbepoetin alfa. Subjects received 20,000 Units (U) epoetin alfa subcutaneously (SC) every two weeks; 30,000 U epoetin alfa SC every 3 weeks; or 40,000 U epoetin alfa SC every 4 weeks.