In the present paper the A. A. reviewed the more fundamental problems in the ethiopathogenic process of bacterial endocardits and report the bacte¬riological observations done by them in 20 cases of the disecase observed at the Section of Pathological Anatomy and Bacteriology of the Hospital S. Francisco de Assis in charge of the Instituto Oswaldo Cruz. The A.A. isolated Pneumococcus from 10 out the 20 cases, Gonococcus from 2, Staphylococcus from 2, Streptococcus from 5 and Friedlaender bacil¬lus from 1 . The A.A. mainly lay stress on the necessity of the bacteriological exa¬minations being made by a specialist, owing to the difficulties sometimes met with and to the consequences of a detailed examination of the isolated germ.