Methods of electrophoresis in polyacrylamide gel in the system of sodium dodecyl sulphate (SDS-PAGE) with immunoblotting were used to investigate heterogeneity of lipopolysaccharides (LPS) of Ralstonia solanacearum (ICMP 8110, 767, 5712, 7955, 7945, 7944, 8089 and 4157) which were characterized by various type structure of O-specific polysaccharides chains. When carrying out SDS-PAGE, it was determined that LPS of all the investigated strains display bimodal distribution, typical of S-form LPS and include two types of molecules: high-molecular S-fraction and low-molecular R-fraction of LPS. It was shown, that LPS within one serogroup are characterized by such electrophoretic distribution, but in comparison with other serogroup--electrophoretic distribution is individual. The zones of serological activity of LPS as to homological and heterological O-antisera were revealed under immunoblotting. It is shown that the foreseen concentration of general antigenic determinants is observed in S- and SR-zones of LPS represented by O-chains of different length. The results obtained have confirmed the division of the strains under investigation into five serogroups which were found before in a number of serological investigations and evidence for immunochemical heterogeneity of the species R. solanacearum.