In this work the authors have constructed a clinical epidemiological score system for characterizing the severity of the diseased state of our 85 patients got over myocardial infarction. The important role is commonly known which is played by the free radical processes in the pathogenesis of the heart infarct. From these free radical reactions the authors have focused their attention to studying the lipid peroxides. Beside the determinations of the malondialdehyde content of native serums they have measured the intensity of the malondialdehyde development in the free radical system generated by hydrogen-peroxide in vitro treatment of serums. With the help of the newly elaborated and applied method they have obtained a 67.11% average increase of the amount of malondialdehyde developed in vitro in comparison with the mean malondialdehyde value measured in the same analytical conditions with 154 healthy controls. They have made a statistical calculation for studying the question if there is any relationship between the scores of the age of patients and the malondialdehyde values of hydrogen-peroxide treated serums. On the basis of results of biochemical measurements and statistical analyses it seems very important to pay more attention both to the intensity of free radical reactions and the patients age in the severity's relations of the diseased state at heart infarct patients.