New menaquinones have been isolated from Oerskovia turbata and Brevibacterium lipolyticum in the nocardioform and coryneform groups of bacteria, which have been identified to be a series of menaquinones with a tetrahydrogenated isoprenoid chain, designated as menaquinone-9(H4) and menaquinone-8(H4), respectively, by thin layer chromatography, ultraviolet and infrared spectrophotometry and mass spectrometry. The nuclear magnetic resonance spectra of the quinones have revealed that all the two saturated dolble bonds occur in the internal units of the isoprenoid side chain.