This two arm study will compare the maintenance of hemoglobin levels, safety and tolerability of once every 4 weeks subcutaneous administration of Mircera versus epoetin beta in dialysis patients with chronic renal anemia. Patients will be randomized to receive either subcutaneous Mircera (starting dose 120, 200 or 360 micrograms) every 4 weeks or subcutaneous epoetin beta in accordance with the prescribed dosing information. In both groups, the starting dose will be the same as the previous dose of epoetin beta administered in the week preceding first study drug administration. Patients will be treated for 28 weeks with follow up 4 weeks after the last treatment visit. The anticipated time on study treatment is 3-12 months, and the target sample size is 100-500 individuals.

Inclusion Criteria:

• male or female patients, >=18 years of age;
• chronic renal anemia;
• Hb concentration 10.0 - 12.0 g/dL during the screening period;
• continuous subcutaneous maintenance therapy with epoetin at the same dose AND same dosing interval for at least 12 weeks before and throughout screening.

Exclusion Criteria:

• blood transfusion within the previous 8 weeks;
• poorly controlled hypertension;
• significant or acute or chronic bleeding;
• active malignant disease;
• congestive heart failure (NYHA Class IV).