AbstractIn this paper different examples of the effect of coordination‐unsaturated metal compounds on the radical homo‐ and copolymerization of vinyl monomers are considered and analyzed. In all known cases homopolymerization proceeds according to the usual addition chain radical scheme and involve an initiation step with the formation of a primary radical. Complexed radicals or monomers take part in the chain propagation steps. In the case of copolymerization, a complexing agent can considerably influence apparent relative activities of monomers, decreasing or increasing the tendency to alternation. If two monomers are present in the system, one of which forms a complex with a Lewis acid, and the other is a donor with respect to this complex, the formation of a ternary donor‐acceptor complex also occurs in a number of cases. A ternary complex can fulfill the monomer function in the chain propagation reaction, i.e., it can add to the propagating chain as an independent kinetic species. In such cases, strictly alternating copolymers may be obtained. All mechanisms considered agree with the addition‐polymerization scheme. From the kinetic point of view the ternary complex addition is somewhat similar to an elementary step of Butler's inter‐intramolecular cyclopolym