When studying a small group of mollicutes which interact in different way with the host organism (Mycoplasma fermentans PG18--is considered a commensal of the human urogenital tract, and sometimes manifests as AIDS cofactor, Acholeplasma laidlawii PG8 is saprophytic but it is connected with various pathologies in human organism, A. laidlawii var. granulum 118--agent of the yellow of cereals--palegreen dwarfness) the author has found the carbohydrate composition of their cell surface. Glycocalix of all three representatives proved to be rather various. Biochemical investigation methods were used to establish the presence of galactosamine, glucosamine, minor quantity of rhamnose, ribose, arabinose, xylose, mannose as well as considerable share of fucose, galactose, glucose. Qualitative and quantitative content of monosaccharide composition of the glycocalix of certain species of mollicutes which have different ecological niches is studied in the work and the role of some sugars in performing certain important functions is discussed.