This article compiles the papers dealing with the biochemistry of chitin synthase (CS) published during the last decade, provides up-to-date information on the state of knowledge and understanding of chitin synthesis in vitro, and points out some firmly entrenched ideas and tenets of CS biochemistry that have become of age without hardly ever having been critically re-evaluated. The subject is dealt with under the headings "Components of the CS reaction" (educt, cation requirement and intermediates; product), "Regulation of CS" (cooperativity and allostery; non-allosteric activation or priming of CS; latency), "Concerted action of CS and enzymes of chitinolysis", "Inhibition of CS", "Multiplicity of CSs", and "Structure of CS" (the putative UDPGlcNAc-binding domain of CS; identification of CS polypeptides; glycoconjugation). The prospects are outlined of obtaining a refined three-dimensional (3D) model of the catalytic site of CS for biotechnological applications.