Background and objectives: This study examined the efficacy of C.E.R.A., a continuous erythropoietin receptor activator, for correcting anemia in patients who had chronic kidney disease (CKD) and were not on dialysis.Design, setting, participants, & measurements: In this open-label, randomized, parallel-group, Phase III study, 324 adult patients with CKD not on dialysis nor receiving treatment with erythropoiesis-stimulating agents (ESAs) were randomly assigned (1:1) to receive subcutaneous C.E.R.A. once every 2 wk or darbepoetin alfa once weekly during an 18-wk correction period and a 10-wk evaluation period. Thereafter, patients receiving C.E.R.A. were randomly assigned to C.E.R.A. once every 2 wk or once monthly, and patients receiving darbepoetin alfa could receive darbepoetin alfa once weekly or once every 2 wk for a 24-wk extension period. Dosage was adjusted to achieve a hemoglobin (Hb) response and to maintain Hb ؎1 g/dl of the response level and 11 to 13 g/dl. Primary end points were Hb response rate during correction and evaluation and change in Hb concentration between baseline and evaluation.Results: Hb response rates were 97.5% for C.E.R.A. and 96.3% for darbepoetin alfa. Adjusted mean changes in Hb from baseline to evaluation were 2.15 g/dl (C.E.R.A.) and 2.00 g/dl (darbepoetin alfa). Analysis showed that C.E.R.A. once every 2 wk was as effective as darbepoetin alfa once weekly for correcting anemia. Hb levels remained stable in all groups during the extension period. C.E.R.A. and darbepoetin alfa were well tolerated.Conclusions: Subcutaneous C.E.R.A. once every 2 wk corrects anemia in ESA-naïve patients who are not on dialysis.