PRIOR to the introduction of chemotherapy and antibiotics, bacterial endocarditis was almost always a fatal disease.1 During the past ten years cure rates of 66% to 83% for the subacute forms have been reported, indicating a far better prognosis for patients with this disease today.2,3 At the Philadelphia General Hospital a previous study showed a significant decrease in the number of patients dying with bacterial endocarditis during a recent ten-year period.4 Despite these findings and improved methods of therapy, the incidence of 9.6 patients with bacterial endocarditis per 1,000 autopsies performed at this institution is indicative of a considerable fatality rate. This observation, coupled with the deaths of several patients on the medical wards during the past year in whom bacterial endocarditis was totally unrecognized, led to the present study of 159 patients hospitalized at the Philadelphia General Hospital with this disease from 1954 to 1963. Special