THERE HAS been an increase in recognized human infections caused by the Mimeae group of organisms, which were first named and described by De Bord, in 1939.1These organisms have been isolated principally from the urinary tract and also from the blood, spinal fluid, soft tissues, pleural fluid, ascitic fluid, and other body specimens. Their special significance is that they may be morphologically identical to the Neisseria organisms. In contrast to the Neisseria organisms, the Mimeae group are not sensitive to the commonly used antibiotics, and consequently it is extremely important to identify these organisms correctly and use the most effective antibiotic in each particular instance. A case of an apparently healed bacterial endocarditis due to Herellea vaginicola superimposed upon a rheumatic endocarditis is described. A 19-year-old Negro private was admitted to a military hospital June 5, 1955, with a four-day history of substernal chest pain which was accentuated