Enzyme ? mediated polymer synthesis in non-natural environments has significantly expanded in scope and impact over the past 10 years. This review focuses on a rapidly expanding research activity where in vitro enzyme catalysis is used for the synthesis of polyesters, polycarbonates, polyphenols, vinyl polymers, as well as natural and artificial oligosaccharides like cellulose, amylose, xylan, and chitin. The inclination to use enzymes for polymer synthesis has been fuelled by a desire to carry out these reactions in the absence of heavy metal-based catalysts, under mild conditions and with high selectivity. The aspects of this work that include enzyme-catalyzed step-growth polycondensation, chain-growth ring-opening polymerizations, oxidation polymerization and corresponding transesterification of macromolecular substrates are discussed. The polymerization utilizes mainly hydrolases and oxidoreductases as catalysts. Characteristic features of enzymatic polymerizations are also discussed.