Dextransucrase catalyses the synthesis of a-D-glucopyranosyl homopolymers and oligomers from sucrose as a substrate. This paper is a review of reports on the mechanism of dextran and oligosaccharides synthesis. The presence of a low molecular acceptor dextran (3-20 kDa) or low molecular acceptor sugars in reaction mixtures enables obtaining of dextran with molecular weight in a range from 30 to 80 kDa or oligosaccharides with low d.p., which have gained increased nutritional interest (prebiotics). In these reactions, the hydrolytic enzyme, i.e. dextranase, may be involved together with dextransucrase instead of acceptors.