The results of studies of polyelectrolyte complexes The results of studies of polyelectrolyte complexes of chitosan are summarised and described systematically. of chitosan are summarised and described systematically. Chitosan complexes with biopolyelectrolytes, with modified Chitosan complexes with biopolyelectrolytes, with modified natural polyelectrolytes and with synthetic polyanions natural polyelectrolytes and with synthetic polyanions are considered. Medical and biotechnological applications are considered. Medical and biotechnological applications of chitosan complexes are discussed. The bibliography of chitosan complexes are discussed. The bibliography includes 156 references includes 156 references. .