In this prospective, multi-center, observational study, non-dialysis CKD patients with anemia who were naïve to erythropoiesis-stimulating agents (ESAs) were divided into three groups based on their Hb levels at initiation of epoetin beta therapy (Group I: 10 ≤ Hb < 11 g/dL, Group II: 9 ≤ Hb < 10 g/dL, and Group III: Hb < 9 g/dL). This evidence concerns the gene GSTM1 and chronic kidney disease.