The lipopolysaccaride of Chlamydophila psittaci 6BC was isolated from tissue culture-grown elementary bodies using a modified phenol/water procedure followed by extraction with phenol/chloroform/light petroleum. Compositional analyses indicated the presence of 3-deoxy- dmanno-oct-2-ulosonic acid, GlcN, organic bound phosphate and fatty acids in a molar ratio of ≈ 3.3:2:1.8:4.6.