This work was planned to study biochemical characters for R. solanacearum lipopolysaccharide (LPS) and its relation to virulence. All tuber isolates were highly virulence compared with soil and water isolates. These isolates were divided into two groups according to disease incidence and disease severity; the first group contained virulent isolates which isolated from tuber samples and the second group contained avirulent isolates which isolated from soil and water samples. Virulent isolates showed high content of either lipopolysaccharide or total sugars in LPS compared with avirulent isolates. Total sugars in LPS were determined using gas liquid chromatography (GLC). The glucose was the major content of R. solanacearum lipopolysaccharide in all examined isolates. Lipopolysaccharide for virulent isolates of R. solanacearum showed high amount of arabinose, xylose, mannose and galactose compared with the avirulent isolates, while the amount of mannitol was the highest in   Lipopolysaccharide for avirulent isolates compared with virulent isolates. There is no significant difference for the amount of rhamnose, fructose and sorbitol in lipopolysaccharide for all isolates.