Abstract <p>The features of controlled radical polymerization of styrene and its copolymerization with acrylonitrile, proceeding by the atom transfer mechanism under the action of catalytic systems simultaneously containing two copper complexes (CuBr₂/TPMA and CuBr₂/Me₆TREN), have been investigated. The possibility of using low concentrations of the catalyst and the use of sodium potassium tartrate (Rochelle salt), as well as isopropylamine as reducing agents, in the controlled synthesis of the (co)polymers has been evaluated. It has been established that the proposed systems can effectively catalyze the polymerization of styrene and its copolymerization with acrylonitrile. The course of polymerization is accompanied by a linear increase in the molecular weight of samples with conversion, which is characteristic of controlled radical polymerization processes. It has been shown that polar solvents should be used for the process to be efficient. The optimal catalytic systems that allow the process to be carried out at high rate while maintaining control over the process have been identified.</p>