p-Nitrophenyl beta-chitobioside (2) was prepared from p-nitrophenyl 2-acetamido-2-deoxy-beta-D-glucopyranoside (1) using beta-N-acetylhexosaminidase from Aspergillus oryzae. As minor by-product a (1-->6)-linked regioisomer (3a) was formed. Addition of (NH4)(2)SO4 and organic co-solvents (acetonitrile, dioxane) substantially increased the yield.