The frequent occurrence of anemia in bacterial endocarditis has not been sufficiently emphasized. Recognition of this association is particularly important in cases in which the use of antibiotic therapy for an undiagnosed febrile illness may have masked some of the usual symptoms and signs of the disease. Anemia and other hematological disturbances may occasionally even overshadow the more familiar manifestations of bacterial endocarditis to such a degree that the disease may be mistaken for a primary hematological disorder. Since antibiotic therapy cures most cases of subacute bacterial endocarditis, it is important that the diagnosis of anemia be made correctly and as early as possible. The occurrence of anemia along with bacterial endocarditis is usually mentioned in descriptions of the disease. In 1927 Pepper1reported anemia in 19 of 20 cases of subacute bacterial endocarditis caused by nonhemolytic Streptococcus viridans. In 1939 Middleton and Burke2reported anemia, usually of