Coronary artery bypass grafting was performed under extracorporeal circulation on 16 ischemic patients, with the protease-inhibitor balance being investigated by determining the level of neutrophilic elastase, alphal-antitripsin, alpha2-macroglobulin and the indicators of lipid peroxidation (malonic dialdehyde and catalase activity) at different stages of the disease. It was found out that the development of the inflammatory response to surgical intervention and extracorporeal circulation was accompanied by a decrease in the protease-inhibitory potential in patients being operated against the background of a considerable increase in the level of neutrophilic elastase and activation of lipid peroxidation processes, with the proteolysis-antiproteolysis system rebalanced by the 3rd day of the postoperative period.