The results indicate that the chief polysaccharides of N. crassa hyphal walls are chitin and glucan containing a preponderance of [beta]-1,3-linkages. Almost half of the bound glucose can be converted to the free monosaccharide by means of [beta]-1,3-glucanase alone. The possible existence of another glucan with linkages not affected by [beta]-1,3-glucanase or of a nonchitionous acetylhexosamine polymer can not be ruled out at this stage.