A typical case of subacute bacterial endocarditis is characterized clinically by a septic temperature, physical signs of valvular heart disease, evidence of embolic processes (petechiae, embolic glomerulonephritis, etc.), and a positive blood culture (streptococcus). There is often a secondary anemia and moderate enlargement of the spleen, and death usually results within two years. On the other hand, the characteristic features of acute rheumatic endocarditis are acute arthritis, fever, evidence of valvular heart disease, absence of embolic processes, and a tendency to recover with or without a valve defect. Typical instances are therefore easily distinguished clinically, but there are many cases in which the diagnosis is uncertain. The transition from the acute rheumatic to the subacute bacterial type may be so gradual that it is impossible to say where the one ends and the other begins. The following history illustrates such a case: REPORT OF CASE A white girl, aged 23,