By means of ultrasonication two fractions of the carboxymethylated chitin-glucan complex isolated from the cell walls of the filamentous fungus Aspergillus niger were obtained. Elemental analysis as well as C-13 NMR investigation of the high-molecular weight (M-w 680 kDa) and low-molecular weight (M-w 75 kDa) fractions revealed their essentially different chitin content. HPLC analysis of the fractions produced by ultrasonic treatment of different duration, combined with nitrogen assay showed steadily increasing chitin content in the faster eluted fraction that allows one to suggest the different susceptibility of the two components of the chitin-glucan complex to the ultrasonication.