The myocardium was ultrastructurally investigated immediately after 12 weeks of feeding in one part of the animals and in the remaining animals 27--30 months after termination of the feeding period. At the same time, parameters of the myocardial contraction were measured immediately after the feeding at isolated trabeculae of the left ventricle and 27--30 months after the termination of the feeding at the left ventricle in situ. After the 12 weeks of feeding the morphometrically estimated intracellular lipid content rises from 0.23% (normal) to 5.26%. The mitochondria decline from 36.98% (normal) to 29.08%. The sarcoplasmic reticulum (SR) changes in a vesicular or vacuolar manner respectively. The contractility index Vmax of isolated trabeculae decreases insignificantly. The resting potentiation and the diastolic stiffness are increased. 27--30 months after termination of feeding the lipid content and the mitochondria are normal in comparison to controls of the same age. The vacuolar changes of SR and its cellular portion are increased. The contractility index of the heart in situ max (dp/dt)/P is decreased insignificantly. The velocity of relaxation is enhanced in comparison with controls. By comparing ultrastructural and functional findings it can be seen that variations in the contraction performance are accompanied by stronger changes of the cellular structure immediately after the feeding than 27--30 months after the termination of the feeding. At this time continuing small alterations in the contraction performance of the heart in situ are observed in addition to the reversibility of various characteristics of damage together with an increase in the Ca++-transporting SR and its alterations.