The present paper aimed to investigate a possible effect of the antioxidant butylhydroxyanisole (BHA) on the extent of experimental necroses of the myocardial cells. Administration of BHA in a daily dose of 10 mg.kg-1 i. m. lasted 20 days. The isoprenaline model in a single-dose subcutaneous administration of IP 25 mg.kg-1 was used to induce experimental necrosis. Tables 1-7 show quantification and morphometry of histological and electron-microscopic images. The protective effect of BHA was manifested by influencing the extent of myocardial necroses (p < 0.01) (Table 1). In the morphometric electron-microscopic examinations, the protective influence of BHA was recorded in the parameter of cristolysis, i.e. equipment of mitochondria with cristae (Table 5), in comparison of the control group with IP and the BHA group with IP (p < 0.01). No statistically significant differences in the two above-mentioned experimental groups were found in the other compartments.