The organisms usually responsible for subacute bacterial endocarditis are of a low degree of invasiveness and are frequently or regularly present in the flora of the body cavities during health. Nonhemolytic streptococci, enterococci, influenza bacilli, and coagulase-negative staphylococci are most commonly recovered from the blood in such patients. Gram-negative, non-sporeforming, anaerobic bacilli of the genus Bacteroides are readily isolated from materials obtained from the nasopharynx, colon, and vagina in many persons. It is well known that they may cause serious suppurative disease, but are a rare cause of subacute bacterial endocarditis.1 This report describes a case in which a diagnosis of Bacteroides endocarditis was established, and in which therapy with terramycin was successful. REPORT OF CASE Mrs. A. V. was admitted to the hospital in January, 1950, for study of a febrile illness of nine months' duration. She had had rheumatic fever on two occasions (at the ages of