For the first time, electron-microscopic morphometric analysis of the mitochondrial system in cardiomyocytes of the left ventricle was performed in rats exposed to hypergravity (2G) After five days of exposure, the number of long mitochondria sharply increased in the interfibrillar zone of cardiomyocytes. The numbers of inter-mitochondrial junctions (IMJ) were increased in all zones of mitochondria localization. The ultrastructure and numerical density of mitochondria remained within the normal range. Similar changes were also revealed on day 19 (the end of exposure), but the numbers of IMJ in the perinuclear and subsarcolemmal perivascular zones were lower than on day 5. One months after the end of 19-day exposure at 2G, the test parameters of the mitochondrial system did not return to the norm. Apparently, this is why the repeated exposure to hypergravity (2G for five days after 30-day rest) failed to evoke a similar response from the mitochondrial system of cardiomyocytes.