[en] The N-acetylhexosaminidase (referred as Str) secreted by Streptomyces albus G. has been purified by zone electrophoresis. It is slightly less basic than egg-white lysozyme. Its isoelectric point is close to pH 10.3. It has no action on the [alpha]- and [beta]-phenylglycosides of N-acetylglucosamine and on the disaccharides [beta]-(1-4)-di-N-acetylglucosamine (di-N-acetylchitobiose) and [beta]-(1-6)-N-acetylglucosaminyl-N-acetylmuramic acid but it splits the tetrasaccharide [beta]-(1-4)-tetra-N-acetylglucosamine(tetra-N-acetylchitotetraose) in di-N-acetylchitobiose. Contrary to lysozyme, it does not split the tetrasaccharide O-[beta]-N-acetylglucosaminyl-(1-6)-O-[beta]-N-acetylmuraminyl-(1-4)-O-[beta]-N-acetylglucosaminyl-(1-6)-[beta]-N-acetylmuramic acid in disaccharide by hydrolyzing the [beta](1-4) linkage. In those conditions the disaccharide liberated, as well as the tetrasaccharide, from Microccus lysodeikticus cell walls after incubation with the N-acetylhexosaminidase Str, can not be put down to a further digestion of some tetrasaccharidic fragments. A chitobiase only active on the [beta]-phenyl-glycoside of N-acetylglucosamine and on the di-N-acetylchitobiose is also present in contentrated culture filtrates. It is a protein acid at pH 6.6.