As the myocardium in patients with dilated cardiomyopathy (DCM) is deteriorating progressively, resulting in a decrease in left ventricular function, patients with end-stage DCM may require implantation of a left ventricular assist device (LVAD) unless they undergo heart transplantation. Although LVAD has been reported to provide excellent hemodynamic support, no data are currently available about the effects of long-term LVAD support on the myocardium in patients with DCM. We describe two patients with end-stage DCM who underwent LVAD implantation and were supported with LVAD for 524 and 245 days, respectively. Serial myocardial biopsies showed increases in myocardial cell diameter and intercellular fibrosis, despite excellent hemodynamic support by LVAD. These data suggest that the myocardium in patients with end-stage DCM deteriorates progressively, even if the pre-load of the left ventricle is reduced by LVAD.