Extracellular beta-N-acetylhexosaminidase in basic specific activity 1.5 U/mg protein was induced 15 - 35 times (up to 50 U/mg protein) by mixture of chitooligomers (crude chitin hydrolysate), 10 - 20 times (20 - 30 U/mg protein) by N-acetylglucosamine, and 10 times (14 U/mg protein) by chitosan in Aspergillus oryzae. Addition of NaCI (15 - 23 g/l) to the cultivation medium enhanced the induction in 10 - 20%.