The inotropic response of the myocardium to extrasystolic treatment was studied on isolated perfused papillary muscles from rats with postinfarction cardiosclerosis. The development of postinfarction cardiosclerosis was accompanied by a decrease in myocardial excitability. The amplitude of extrasystolic contractions in the remodeled myocardium far surpassed the control. However, the amplitude of postextrasystolic contraction did not surpass that in normal contraction-relaxation cycle. Our results suggest that the ability of the sarcoplasmic reticulum in cardiomyocytes to accumulate Ca2+ is impaired during postinfarction remodeling.