The occurrence of infective endocarditis in patients with habitual alcoholism is fairly frequent. A high percentage of patients with idiopathic dilated cardiomyopathy are habitual alcoholics. Yet, the occurrence of infective endocarditis in patients with idiopathic dilated cardiomyopathy is extremely rare. Such was the case, however, in the patient to be described below. A.W., a 60-year-old man, had been a habitual alcoholic for many years and had the onset of chronic congestive heart failure (CHF) at age 53. About a year before death periodic ventricular tachycardia with syncope occurred and he had 2 episodes of ventricular fibrillation with successful resuscitation. The ejection fraction was 19%. His final hospitalization was precipitated by worsening CHF. The blood pressure was 100/80 mm. Hg., and the temperature, 37 C. A grade 3/6 systolic blowing murmur was heard over the cardiac apex. Four of 4 blood cultures grew Staphylococcus aureus and chest radiograph showed an infiltrate consistent with acute pneumonia in each lung. Death was attributed to progressive CHF and pneumonia. At necropsy, the heart weighed 595 grams. The coronary arteries were virtually devoid of atherosclerotic plaques. A thrombus was present in the right atrial appendage. All 4 cardiac chambers were dilated, particularly the ventricles. Several mural endocardial white plaques were present in the left ventricle. A vegetation measuring about 1 cm. in maximal diameter and consisting of colonies of Gram-positive-organisms, pus, and fibrin was present on the atrial aspect of the posterior mitral leaflet. The underlying leaflets and chordae tendineae were normal.