Background: Little is known about the relationship between exercise intolerance and lipid peroxidation in chronic heart failure (CHF) patients. This study was designed to investigate the relationship between exercise-induced plasma malondialdehyde (MDA) changes in CHF patients and to determine whether there is any association between plasma MDA levels and exercise capacity assessed by cardiopulmonary exercise testing. Methods: Cardiopulmonary exercise testing was applied to 31 CHF patients (16 ischemic, 15 idiopathic) and controls. Rest and peak exercise blood samples were analyzed for MDA. Results: Patients with CHF had elevation of plasma MDA levels during exercise compared with controls (p < 0.001 vs. p = 0.588). MDA change remained significant both in ischemic and idiopathic cardiomyopathy groups (p < 0.05 and p < 0.01, respectively). ΔMDA (peak exercise MDA – rest MDA) showed significant inverse correlation with peak oxygen consumption in patients with CHF. Conclusion: Lipid peroxidation is increased in patients with CHF during exercise regardless of etiology, and this increase is inversely related to oxygen consumption.