The mortality rates in these different subgroups of endocarditis are given. In the preantibiotic era, when there were no prosthetic valves and few addicts, NVE was the sole variety of endocarditis and was an almost universally fatal disease. During the past 35 years since the introduction of penicillin, the mortality rate of NVE has changed little and has ranged from about 20 to 40%. In contrast, the mortality rate in PVE is higher, ranging from 23 to 60%, and the mortality rate in addict endocarditis is lower, ranging from 0 to 28%. Thus, the outcome in endocarditis varies, depending on the pathogenesis of the infection and the type of valve involved. The outcome also appears to be influenced by age of patient, presence or absence of underlying disease, causative microorganism, specific valve(s) involved, and complications, both intra- and extracardiac, especially heart failure and renal failure. Finally the outcome is influenced by several issues specifically related to therapy, including early diagnosis and initiation of antibiotics, appropriateness and adequacy of antibiotic regimen, and an aggressive combined medical-surgical approach in selected situations. These issues relevant to the therapy of infective endocarditis will serve as the focus for the subsequent discussion.