Biotechnological applications using immobilized systems have recorded fast development in last years. The paper tries to deal with chemical aspects of immobilized biotechnologies. It is aimed primarily at definition of immobilization techniques and their modifications. For every method, the principle of immobilization and the most frequently used carriers are described. The appropriate matrix materials such as agar, agarose, k-carrageenan, alginate, pectates, protein carriers, chitosan, polyacrylamide and other synthetic carriers are characterized more in detail. Basic principles of covalent coupling are presented as chemical equations. Several examples of applications of immobilized systems in both food and non-food biotechnological processes are mentioned.