Lipopolysaccharides (LPS) from Legionella feeleii serogroup 1, L. hackeliae serogroup 1 and L. jordanis were subjected to chemical analysis. All three LPS contained D-mannose, D-glucose, D-glucosamine, L-glycero-D-manno-heptose, 2-keto-3-deoxyoctonic acid and glycerol. In addition the LPS of L. feeleii was characterized by L-quinovose (tentatively identified) and L-fucosamine, L. hackeliae LPS by D-quinovosamine, D-galactosamine and D-galacturonic acid, and L. jordanis LPS by D-quinovosamine. Phosphorylated sugars were detected in all three LPS. The backbone sugar of the lipid A part was in each case 2,3-diamino-2,3-dideoxy-D-glucose substituted with a complex pattern of fatty acid, including 20-22 different amide-linked (non-branched and methyl-branched) 3-hydroxy fatty acids of chain-length ranging from 12 to 23 carbon atoms. The fatty acid patterns included also ester-linked nonhydroxylated entities and the uncommon 27-oxo-octacosanoic acid and 29-oxotriacontanoic acid. The LPS of L. hackeliae and L. jordanis also contained heptacosane-1,27-dioic and nonacosane-1,29-dioic acid, and their 2-hydroxy analogues were characteristic of L. jordanis LPS. SDS-PAGE patterns of the three LPS were distinctly different. Both L. feeleii and L. jordanis produced smooth-form LPS with characteristic ladder patterns, whereas L. hackeliae LPS were of more rough-type character.