A left ventricular (LV) thrombus grew rapidly over chronic endocarditis 2 months after anterior myocardial infarction. Echocardiograms demonstrated a rapidly growing LV thrombus an eventual obstruction. Despite anticoagulant/thrombolytic therapy, the patient died of acute LV failure. Histopathologically, a fresh thrombus overlay thickened endocardium with massive T lymphocyte infiltration over healed infarction.