THE crystal structure of N-acetylglucosamme, C8H15O6N, has been investigated in connexion with the work on lysozyme proceeding in this laboratory1. Salton2 and others have shown that N-acetylglucosamine is a basic constituent of the bacterial cell walls of Micrococcus lysodeikticus, the most commonly used substrate of lysozyme (muramidase), and Wenzel et al.3 have reported that this compound inhibits the action of the enzyme. At a later stage it is hoped to relate the structure to those of lysozyme and its substrates in detail.