Three allyl ethers, viz. the ethyl, 2-hydroxyethyl and phenyl compounds, have been examined as additives in radical polymerizations of styrene (STY), methyl methacrylate (MMA) and acrylonitrile (ACN) at 60°C using azobisisobutyronitrile as initiator. As retarders and transfer agents, the ethers are considerably more effective with ACN than with the other monomers. Allyl phenyl ether engages in significant copolymerization with ACN and slight copolymerization with MMA; there is negligible incorporation in polySTY.