Procedures for the synthesis of guanidine metacrylate and guanidine acrylate, the new monomeric salts of vinyl monomers of the acrylic family with guanidine, were developed. Their structure was proved by H-1 NMR, IR, and elemental analysis data. It was shown that the prepared monomeric salts are capable of (co)polymerizing in an aqueous medium via the radical mechanism. It was found that, in the case of copolymerization of guanidine salts with N,N-diallyl-N,N-dimethylammonium chloride, copolymers enriched in the (meth)acrylate Component were produced over the entire range of reactant-solution composition examined. The reactivity ratios for these copolymer pairs were determined.