PHOTOSENSITIZED polymerization is one of the methods making it possible to use visible and long-wave UV light for the synthesis of polymers. I t has been shown that organic compounds belonging to various classes may be used as sensitizing additives. However, the action of some simple substances such as the halogens on the photopolymerization of vinyl monomers has not been investigated. I t is known that when halogens are irradiated with visible light, they are decomposed into free atoms. On this phenomenon are based the photo-reactions of halogens with organic compounds [1]. I t may be assumed that under certain conditions and ratios of the reactivities of an unsaturated compound and a free halogen atom, the latter will initiate a polymerization reaction by the scheme: