Chemical depolymerization of glucosaminoglycans with nitrous acid solubilized alkali-insoluble glucan from the walls of the basidiomycetes Schizophyllum commune and Agaricus bisporus but not from the walls of the ascomycetes Aspergillus nidulans and Neurospora crassa. In all four fungi depolymerization of glucosaminoglycans with chitinase was effective at converting a considerable portion of the alkali-insoluble glucan into a water/alkali-soluble form. This indicates chemical linkage between glucosaminoglycan (chitin) and (3-glucan in these fungi.