Abstract Galactoglucomannans from Dactylium dendroides, strain NRRL 2575, and from the galactose oxidase-producing mold originally described as Polyporus circinatus were structurally characterized. The purified galactoglucomannans were homogenous according to cellulose acetate paper and polyacrylamide gel electrophoresis experiments. The major monosaccharide constituents were d-mannose, d-galactose, and d-glucose. Methylation analysis, Smith degradation, graded acid hydrolysis, and 1H-NMR and 13C-NMR spectroscopy were employed to determine the polysaccharide structures. The immunologic and chemical data showed that the polysaccharides were structurally different.