The goal in the research of cell therapy is to develop implants containing living allogenic or xenogenic cells to treat disorders caused by the loss of secretory cell function. Cell therapy is based on the concept of immunoprotection, which involves encapsulation of cells or small clusters of tissue in a semipermeable membrane capsule and subsequent implantation of the capsules into the body in order to eliminate a long-term lack of enzymes, proteins, or other biological substances. The semipermeable membrane should permit diffusion of oxygen and necessary metabolites and release of cell secretion products but restrict the transport of large cytotoxic agents of the body's immune system. This function is successfully fulfilled by polymer hydrogels. The review concerns cell microencapsulation, i.e. producing capsules 100-600 m in diameter. The requirements qualifying polymers for cell encapsulation are discussed. Various types of polymers used in cell microencapsulation are reviewed and their pros and cons discussed. Biological tests of hydrogels for cell encapsulations are briefly mentioned.