Morphological changes and regeneration activity of the rats' liver after an experimental myocardial infarction (MI), caused by a permanent left coronary artery occlusion, were investigated. It has been shown that in 6 months after MI there were considerable changes of the rats' liver circulatory system: the quantity of vessels per unit of area increased by 118%, thickness of their walls by 19%, and the average square of vessels lumens by 159%. The percentage of connective tissue in 6 months after MI increased more than in one and a half time in comparison with control. Inflammatory and necrotic changes in rats' liver remained for 6 months after MI. The liver injury caused by MI led to activation of regeneration processes in its parenchyma. In 6 months after MI, the number of 4c- hepatocytes decreased by 12% in comparison with control, and the number of 4c x 2- and 8c-hepatocytes increased by 45 and 71%, respectively. The mean level of hepatocytes ploidy increased in 6 months after MI by 11%. The dry mass of rats' hepatocytes increased in 6 months after MI by 19% in comparison with control. Thus, liver regeneration after MI is more due to hepatocytes hypertrophy than to their polyploidization.