Lipopolysaccharide (LPS) was extracted from cells of Centipeda periodontii ATCC 35019 by a hot phenol-water method, purified by nuclease treatment and by repeated ultracentrifugations. The LPS was composed of 21.7% hexose, 9.1% hexosamine, 10.3% fatty acid, 0.5% protein, 2.5% phosphorus, 4.3%