Oligosaccharides containing a beta-N-acetylglucosamine moiety are useful building blocks for the synthesis of complex substances with important functions in vivo, such as cell recognition, adhesion, and communication. Microbial beta-N-acetylhexosaminidases have been applied to the preparation of a wide range of such biologically significant compounds. In addition, they have been employed for the analysis of complex sugar chains in glycoproteins and glycopeptides, and they have found application as biocontrol agents, particularly against fungal pathogens of plants. This survey compares amino acid sequence data, biochemical characteristics, and catalytic properties of beta-N-acetylhexosaminidases from a number of microbial sources.