The lipopolysaccharide from Klebsiella oxytoca rough mutant R29 (O1 - /K29 - ) has been isolated and its complete structure has been elucidated by compositional analyses, NMR spectroscopy, and laser-desorption mass spectrometry. The carbohydrate backbone has the structure of which the GlcN residues (the lipid A backbone) are acylated by 14:(3-OH) (amide-linked) and 12:0, 14:0(3-OH)(ester-linked) fatty acids.