The review provides current information on five groups of enzymes, involved in the hydrolysis of starch: endo- and exoamylases, debranching enzymes, isomerases, and cyclodextrin glycosyltransferases. Common classification of starch degrading enzymes as well as the names of microbial species producing enzymes and activity properties are presented. Structures of the catalytic domain are shown for the a-amylase superfamily, b-amylase, and glucoamylase. Possible subsite structures of the a-, b-, and glucoamylases active domains are presented and the differences in specificities of starch degrading enzymes are explained in terms of differences in the number of subsites, the values of free energy of interaction between a glucose residue and the subsite, the positioning of the substrate at the enzyme active domain and the positioning of catalytic site in active center. Three kinds of modes of hydrolytic reaction are described: random attack, single chain attack, and multiple attack.