SYNOPSISThe copolymerization of propylene and vinylchloride with a TiCh-EtaAI system is possible in the presence of polar complex-forming additives. The presence of diphenylamine is nessesary but not enough to complete the reaction. If the complex-forming ether-amine mixture has a high mole ratio, the composition of the copolymer can be changed only in a small range. But when the ether-amine mole ratio is low, one can change composition of the copolymer at will. The presence of the complex-forming additives increase the conversion considerably. It is very important that the vinyl chloride be neat. If the vinyl chloride is contaminated with other chlorinated hydrocarbons, the reaction does not take place. If the vinyl chloride has a small acetylene content, it does not disturbe the copolymerization. Several properties of the copolymers change proportional to the composition. The copolymers have lower heat stability than the homopolymers.