An increase in blood level of Cortisol and overproduction of free radicals is present during first days following acute ischemia and myocardial infarction. This increase exceeds the activity of protective compounds and systems of myocardial cells undergoing ischemia. The aim of this work was to study the relationship between the Cortisol blood level and the intensity of free radical reactions in patients with acute myocardial ischemia and acute myocardial infarction with respect to metabolic (glucose, uric acid) and enzymatic agents of ischemia and necrosis. The study was performed in 75 patients (20 females and 55 males) aged 38-75 years, including 13 patients with acute myocardial ischemia (6 females and 7 males) aged 40-66 years (group I), 40 patients with acute myocardial infarction (8 females and 32 males) aged 38-72 years (group II) and 22 healthy volunteers (6 females and 16 males) aged 39-75 years (control group). The concentration of Cortisol in blood and other biochemical determinants were measured on the second, fifth and seventh day following admission to the coronary care unit. The intensity of free radicals reactions was measured by using the concentration of Vitamin C, malondialdehyde (MDA), uric acid and white blood cells (WBC) count as markers. The results obtained have led to the following conclusions: 1. The increase in blood level of Cortisol in acute myocardial infarction is higher in comparison to the level of Cortisol in acute myocardial ischemia. 2. The intensity of free radical reactions during acute myocardial ischemia and acute myocardial infarction can be assessed by the decreased level of Vitamin C, increased level of malondialdehyde, uric acid concentration and leukocyte (WBC) count. 3. There is no correlation between the intensity of free radical reactions and elevation of blood cortisol during both acute myocardial ischemia and acute myocardial infarction. 4. Elevated levels of Cortisol in blood correlate with elevated levels of glucose and uric acid in blood during both acute myocardial ischemia and acute myocardial infarction. 5. Increase in enzymatic markers of ischemia and necrosis during acute myocardial ischemia and necrosis shows no correlation with the intensity of free radicals reactions.