Collagen metabilites were studied in blood end urine of 188 patients with transmural and 200 patients with nontransmural acute myocardial Infarction. Basing on results of repetitive determinations of these metabolites the time of formation of postinfarction cardiosclerosis was derived. The period of time elapsing before supposed cardiosclerosis formation varied from 30 to 65 days depending on the necrosis mass, clinical course of an infarction (with recurrencies, prolonged) and complex of other factors (age, heart failure, ''background'' diseases).