Lipopolysaccharides (LPS) of plant-growth-promoting bacteria of the genus Azospirillum are involved in the initial steps of formation of the association with host plant. This work aimed compositional analysis of the LPS from Azospirillum zeae and Azospirillum formosense. The LPS were extracted from the cells by hot phenolwater solution. Biopolymer composition of the LPS was studied by colorimetric methods. Determination of the fatty acid composition of the lipid A was performed by GLC. O-deacylation of the LPS A. zeae revealed that 3-hydroxyhexadecanoic acid is N-linked, whereas 3- hydroxytetradecanoic hexa- and octadecenoic acids are O-linked. Electrophoretic mobility of the LPS in SDS-PAGE was examined and predominance of the S-form LPS was revealed.