Blood serum antioxidation activity (AOA) was studied by the biophysical method of inhibited electrochemiluminescence in 500 patients with acute myocardial infarction. The degree of increased AOA depends on the size of the affected area. AOA intensity is greater in macrofocal than in microfocal myocardial infarction. It was established that in non-complicated myocardial infarction AOA is characterized by smooth dynamics with normalization of the values on the 3d week. Rapid AOA dynamics are encountered in II or III degree chronic congestive circulatory insufficiency. Protracted dynamics of antioxidation activity (longer than 3 weeks) is evidence of a recurrent character of the disease.