Thirteen cases of infective endocarditis (IE) diagnosed for the first time at autopsy or, in those patients with a previous diagnosis of IE, not thought to be active at the time of death, are presented. Of the six patients who died within 24 h of the onset of symptoms, two died of obstruction of a valve orifice, two died of sepsis, one died of sepsis and alcoholic cardiomyopathy, and one died of a coronary artery embolus. Of the five patients with symptoms lasting more than 24 h, three died of sepsis and congestive heart failure. One died from sepsis alone and one died from congestive heart failure (CHF). In two patients whose duration of symptoms is unknown, one died of sepsis and CHF, and in the other the mechanism of death is unknown. Predisposing factors present in 11 of 13 patients included alcoholism (three), intravenous (IV) drug abuse (three), prosthetic valves (three), aortic stenosis (two), past rheumatic fever (one), and nonstenotic congenitally bicuspid valves (two). The reasons for no antemortem diagnosis were a missed or incorrect clinical diagnosis in three patients seen by a physician shortly before death, no signs or symptoms or found dead (four), non-specific signs and symptoms (three), refusal of medical treatment (one), and a solitary lifestyle (one); there was insufficient information about one patient. Individuals with needle tracks, generalized petechiae, Osler's nodes, splinter hemorrhages, intravenous catheters, pacemaker wires, and infected aortic-valve (A-V) shunts are at risk of IE. Blood and the vegetations should be cultured. The attending physician should be notified of the diagnosis in such cases.