Two O-glycosidically linked acidic polysaccharides, AP I and AP II, were released, respectively, from glycoproteins GP I and GP II of Fusarium sp. M7-1 by alkaline borohydride treatment and purified by gel filtration chromatography. They were found to be apparently homogeneous on gel filtration chromatography and analytical ultracentrifugation. Their molecular weights were estimated to be 8.2 x 10(4) and 3.1 x 10(4), respectively. The various oligosaccharide fragments obtained from AP I and AP II by acetolysis and partial acid hydrolysis were purified by gel filtration chromatography and HPLC. Their primary structures were resolved mainly by NMR spectrometry in combination with methylation mass spectrometry. Analyses of the acetolysis and partial acid hydrolysis products and the 1H-NMR spectrum of AP I and AP II showed that they are analogues. Thus, we propose that the main parts of the acidic polysaccharides have the following structures. [formula: see text] *X, unidentified oligosaccharide chains. The numbers on the left and the numbers in parentheses outside the brackets indicate the approximate number of side chains of AP I and AP II, respectively, the saccharide sequences of which are not specified.