Abstract The compositions of lipopolysaccharides from the photoheterotrophic budding Rhodomicrobium vannielii strains DSM 162, Rm5, E3 and 2/1 are reported. Common constituents of these lipopolysaccharides are glucose, mannose, glucosamine, glucuronic and galacturonic acids, 2-keto-3-deoxyoctonate (KDO) and the fatty acids 3-OH-C16:0, 3-OH-C14:0, C14:0, Δ14-C22:1, aside from strain specific differences. Two different, medium-dependent growth forms of strain DSM 162 are described. The vitamin/ yeast extract-concentration in the medium and/or the growth temperature were found as factors triggering the different growth forms. Lipopolysaccharides of the two growth forms had only quantitative differences in composition. Lipopolysaccharide from swarmer cells of strain Rm5 showed a chemical composition comparable to that of chain cells and from simple cycle cells of the same strain.