Background/Aims: Oxidative stress often occurs in chronic hemodialysis (HD) patients. The objective of our study was to investigate the interrelationship between oxidative stress and the degree of renal anemia. Methods: In 107 consecutive HD patients, serum concentrations of two major aldehydic lipid peroxidation (LPO) products, 4-hydroxynonenal (HNE) and malondialdehyde (MDA), and of protein carbonyls were analyzed as parameters of oxidative stress and related to the degree of renal anemia. Additionally, in 76 patients treated with epoetin long-term changes in the serum levels of aldehydic LPO products were observed. Results: In HD patients, serum levels of HNE, MDA, and protein carbonyls are increased in comparison to controls. The lower the hemoglobin, i.e. the stronger the degree of renal anemia, the higher the serum concentrations of HNE, MDA, and protein carbonyls. The HNE and MDA levels decreased during HD. Long-term studies on the correction of renal anemia by epoetin demonstrated a mitigation of oxidative stress during this therapy. During periods of 1 and 2 years, it was observed that the serum levels of HNE and MDA could be reduced. Conclusion: Chronic renal failure is connected with oxidative stress which correlates with the degree of renal anemia, and the serum levels of aldehydic LPO products could be reduced during correction of renal anemia by epoetin.