Abstract
Many cases of bacterial endocarditis can now be cured rapidly and easily. However, there remains a group of patients in whom the eradication of the cardiac infection presents great problems. Some principles of treating these "tough cases" of endocarditis are outlined by means of illustrative patients. Stress is placed on early diagnosis, isolation of the etiologic microorganism, determination of bactericidal antibiotics or combinations, and use of the serum bactericidal test to establish an adequate dosage regimen.