The structures of many microbial polysaccharides from a wide variety of bacterial species and from some algae, fungi and yeasts have been determined. A number of bacterial polysaccharides have either been adopted as commercial products or have the potential for commercialisation. The biosynthetic mechanisms for production of some of these polymers have also been elucidated and the effects of genetic manipulation have been studied. There is now also a much greater knowledge of structure/function relationships in microbial polysaccharides. While almost all this non-structural data has accumulated from the study of Gram negative species, this background information provides a sound basis from which polysaccharides from Gram positive bacteria can now be developed. (C) 2001 Elsevier Science Ltd. All rights reserved.