The isoprenoid quinone contents of seven strains of "Afipia felis," the type strains of "A. clevelandensis" and "A. broomeae," and reference strains of three unnamed "Afipia" genospecies were determined by reverse-phase high-performance liquid chromatography. The quinone profiles of all "Afipia" strains were essentially identical, with ubiquinone 10 as the major component. The identity of ubiquinone 10 was confirmed by mass spectrometry.