Interaction between lipid peroxidation activation and the antioxidant system was studied in thrombocytes of patients with cardiovascular pathology. Positive correlation between superoxide dismutase activity and malonic dialdehyde content was found in healthy persons, while in patients with unstable stenocardia and acute myocardial infarction an inversion of the correlation parameters occurred. The data obtained may be used for prognosis of heart ischemic disease development.