Isoproterenol, administered intraperitoneally in rats in a dose of 2 mg/kg of body mass for a period of 20 days, induced myocardial hypertrophy. After its stoppage a period of regression occurred, during which the myocardium recovered practically to its initial state. Complex studies of connective-tissue components (collagen, glycosaminoglycans, total nonfibrillary protein, total protein, structural, glycoproteins), metrometric data-the coefficient R (1 g of myocardium/199 g of body mass) and histomorphological investigations were performed. The same studies were done on rats of a control nontreated group and of experimental groups-on the 0 day. 7th, 14th and 42 day. It was established there was a gradual recovery to normal values of collagen, total nonfibrillary protein and the coefficient R, which were highest on the day 0. Progressive diminution, e.g., normalization of both the connective tissue components and of the volume of myocardial cells was found histomorphologically, in which the changes were mostly manifested on the day 0, as well. The complex studies of the connective tissue with isoproterenol MH proved that the changes of MH in this tissue correlated with the stages of MH respectively its regression.