A lipopolysaccharide was isolated by extraction of Aspergillus flavus conidia with 45% phenol at 68-70 degrees C. Quantitative analysis revealed 7% nucleic acids, 5.5% proteins, 46% polysaccharides and 49% liquids, of which 12% were covalently bound. Glucose, mannose, galactose and fucose were detected as monosaccharide components of the polysaccharide moiety by gas chromatography; palmitic acid, stearic acid, oleic acid, linoleic acid and myristic acid were mainly present in the lipidic fraction. This material differs from the bacterial lipopolysaccharides, both in composition of the polysaccharide moiety and representation of fatty acids in the lipidic fraction.