ABSTRACT:A chemical method for the objective and fairly accurate measurement of the degree of experimental myocardial necrosis is described. The method is based on significant differences in the electrolyte composition of healthy myocardium and connective tissue, which permit estimation of the extent of myocardial fibrosis according to the degree of deviation of the myocardial electrolytes from the norm. The applicability of the method was demonstrated in studies of standardized myocardial fibrosis induced in the rat by three adrenergic amines (epinephrine, phenylephrine and isoproterenol), in which the extent of scarring observed with the naked eye and under the light microscope showed good correlation with the degree of persistent ionic shifts in the fibrotic myocardium.This simple method of estimating the degree of myocardial fibrosis by chemical means may aid in animal experimental investigations of the prevention and repair of myocardial injury. It may thus contribute to the development of therapeutic regimens for the prevention and treatment of human heart disease.