This observational study will evaluate patients' perception of treatment with erythropoiesis-stimulating agents in patients with chronic kidney disease not on dialysis. Eligible patients initiated on treatment with Mircera (methoxy polyethylene glycol-epoetin beta) will be followed for 6 months.

Inclusion Criteria:

• Adult patients, >/= 18 years of age
• Patients with chronic kidney disease not on dialysis (with or without previous renal transplantation)
• Treated or not with ESA at time of visit
• Patients for whom the treating physician had decided to initiate Mircera for medical reasons before the commencement of the study
• Initiation of treatment with Mircera at the inclusion visit
• Accepting and able of completing the ESA preference questionnaire

Exclusion Criteria:

• Participation in a clinical trial on anemia
• Treatment with Mircera during the 3 months before inclusion
• Dialysis planned in the next 6 months

Patients with chronic kidney disease not on dialysis (with or without previous renal transplantation), initiating treatment with Mircera, and erythropoiesis-stimulating agent (ESA)-naïve or not