In order to investigate the possible reasons for age-related decrease in myocardium resistance to stress, we carried out a study of lipid peroxidation (LPO) stimulation features in the myocardium of adult (10-12 months) and aged (22-25 months) male Wistar rats during immobilization stress. In our studies of ascorbate-dependent LPO and induced chemiluminescence, we found that immobilization stress is accompanied by decreased efficiency in the induction of free radical processes in the heart of aged rats. An important cause of this phenomenon may be age-dependent changes in the catalytical properties of the cytosolic superoxide dismutase. The pathophysiological consequences of stress-related, age-dependent decreased efficiency of induction of free radical processes in the heart are discussed.