Mycoplasmas recovered from tissue cultures and previously shown to belong to the sterol-nonrequiring group of mycoplasmas have been further characterized. The biological and serological properties of these strains show them to be clearly distinct from Acholeplasma laidlawii and A. granularum, two species of sterol-nonrequiring mycoplasmas recently reclassified. It is proposed that the newly described mycoplasmas be designated Acholeplasma axanthum, sp. n.