The beta-glucans different from cellulose are the most abundant class of polysaccharides. They are found in microorganisms and higher plants as structural entities of cell wall, as cytoplasmic and vacuolar reserve materials, and as extracellular substances. Enzyme systems capable to hydrolyze beta-glucans are produced by different microorganisms. The occurrence and nature of beta-glucanases and their substrates are reviewed. The regulation of biosynthesis of these enzymes, their properties, substrate and product specificities, mode of action and molecular cloning are described. The participation of beta-glucanases in the morphogenetic events of yeast cell is presented. The role and synergism of different types of 1,3-beta-glucanases in microbial cell wall lysis and the potential application for isolation of intracellular materials like proteins, carbohydrates, enzymes and as an analytical tool are discussed in the light of current knowledge.