Various uniform salt forms of an R-form lipopolysaccharide (LPS) extracted from Klebsiella strain LEN-111 (O3-:K1-) were prepared and their ultrastructure was examined. The LPS, which was extracted by the phenol-water method, freed from contamination with RNA by treatment with RNase, and precipitated by addition of two volumes of 10mM MgCl₂-ethanol, was used as the original preparation for uniform salt forms. The original LPS preparation formed a hexagonal lattice structure with a lattice constant of 14.9±0.2nm. The LPS after electrodialysis retained the ability to form a hexagonal lattice structure, although its lattice constant was large (18.7±0.5nm) and the lattice structure of the electrodialyzed LPS was labile at pH 8.0 in contrast to that of the original LPS preparation. The magnesium salt form of the LPS formed essentially the same ordered hexagonal lattice structure (lattice constant of 15.0±0.2nm) as that of the original LPS preparation. The calcium and ammonium salt forms formed a hexagonal lattice structure, but the lattice constants of the calcium and ammonium salt forms were larger (18.6±0.6nm and 19.3±0.4nm, respectively) than that of the magnesium salt form. The sodium and potassium salt forms consisted of freely branching ribbon-like structures with an average width of 13nm and an average thickness of 9nm. The triethylamine salt form consisted principally of short rods (10nm×9-13nm).