The fatty acids present in lipopolysaccharides from Xanthomonas sinensis were identified as decanoic, 9-methyl-decanoic, 2-hydroxy-9-methyl-decanoic, 2-hydroxy-9-methyl-decanoic, D-3-hydroxy-decanoic, D-3-hydroxy-9-methyl-decanoic, D-3-hydroxy-dodecanoic, and D-3-hydroxy-11-methyl-dodecanoic acid. These fatty acids occur in the lipid A component where they are bound through ester and amide linkages to glucosamine residues. All types of fatty acids are ester bound; however, part of D-3-hydroxy-dodecanoic and D-3-hydroxy-11-methyl-dodecanoic acid is also involved in amide linkage. The hydroxyl groups of ester-linked 3-hydroxy fatty acids are not substituted. Similar fatty acid patterns were obtained from lipopolysaccharides of nine other Xanthomonas species.