Abstract: Eight isolates of Ralstonia solanacearum, the causal organism of potato brown rot (bacterial wilt) from Egypt and other European countries were characterized according to their biochemical and physiological properties. The selected bacterial isolates were classified as race 3 based on their virulence on different host plants. Virulence degree of all isolates was high on potato cultivar "Lady Rosetta" except isolates RsIs2 and Rs48. Virulence varied from high to low on potato cultivar "Cara", tomato, eggplant and pepper. Analysis of tested R. solanacearum fatty acid profiles showed two groups; group I contains European isolates with long chains-hydroxylated fatty acids while, the Egyptian isolates presented in group II with short chains. A comparative analysis of fatty acid composition and virulence of tested bacteria gives a possibility to suppose that fatty acids may be play an important role in pathogenicity of R. solanacearum.