Abstract: Four component polymerization initiators for olefinic monomers comprise (1) an oxidizing agent such as hydrogen peroxide, a persulphate, a permanganate, a chlorate, a perchlorate, a bichromate, a bromate, a ceric salt, an oxazirane, an organic peroxide or an organic hydroperoxide, (2) a chelate compound of a metal such as titanium, iron, vanadium, aluminum, tin, manganese, chromium, cobalt, copper, zinc or bismuth in which the metal is not fully coordinated, (3) an electron donor in amount at most equal to that required to complex completely the said metal of the chelate compound, the said electron donor being for example an amine, a monoalcohol, an ether, an aldehyde, a ketone, an imine, an oxime, an amide, a sulphonamide, or a phosphonamide, and (4) a chelate complex or salt which is different from the chelate compound (2) and in which the metal may be for example, copper, iron, magnesium, manganese, chromium, vanadium or tin, the degree of coordination of the said metal being different from that of the met