The effect of cell transplantation into cryodamaged rat myocardium was studied on isolated hearts by increasing functional load to the left ventricle. Transplantation of allogeneic fetal cardiomyocytes improved the function of the left ventricle under conditions of considerably increased preload. Transplantation of autologous mesenchymal stem cells repaired left-ventricular function under conditions of increased pre- and afterload.