Allyl glycidyl ether (AGE), allyl 1,1,2,3,3,3-hexafluoropropyl ether (AFE), allyl 2-naphthyl ether (ANE), 2-vinyl-1,3-dioxolane (2VD) and allyl alcohol (AA) have been examined as transfer agents in the radical polymerization of methyl methacrylate (MMA) at 60°C; the transfer constants are 1.1 10-3, 0.1 10-3, 0.2 10-3, 1.1 10-3 and 0.6 10-3, respectively. AFE and AA barely affect the rate of polymerization: AGE, ANE, and 2VD act as weak retarders. There is no direct correlation between effectiveness as a transfer agent and the extent of retardation for these additives. For copolymerization with MMA (monomer-1), the monomer reactivity ratios r1 are 42 ± 5 and 32 ± 5 for AGE and ANE, respectively; for both cases, r2 is very close to zero; 2VD engages in copolymerization with MMA to a negligible extent. Experiments involving styrene or acrylonitrile gave results consistent with those obtained using MMA.