The study concerns determination of disturbances of the oxidative-antioxidative balance in patients with heart failure. The study group consisted of 37 patients, having the average age of 42.3 +/- 12.3 years, suffering from idiopathic or inflammatory heart failure. The patients have been qualified as degree II/III in accordance with NYHA scale. A statistically significant increase of anty-oxLDL level (254.28 +/- 80.79 vs 196.64 +/- 83.11 mU/ml; p<0.01) and malondialdehyde level (4.86 +/- 1.74 vs 3.71 +/- 1.19 micromol/l; p<0.05) has been demonstrated after 6-month observation. No statistically significant differences have been found for the activity of total superoxide dismutase (SOD) and its isoenzymes--(SOD-Mn) and (SOD-ZnCu). The results of the study indicate that no changes in SOD activity and increase in lipid peroxidation products level may lead to generation of oxidative stress may play an important role in the pathogenesis of heart failure.