The radical homo-and co-polymerization of 2,2,6,6-tetramethyl piperidinyl methacrylate (TM-PM) with various initiators have been studied. It was found that, with azo-type initiators, the poly-merization proceeded readily, while with acyl peroxide initiators, the polymerization was inhibitedeffectively because of the formation of the stable TMPM-oxyl radical, identified by ESR. Thisobservation was further confirmed by the absence of inhibition effect on the addition of 2,2,6,6-tetramethyl 4-piperidinol to the polymerization system,whereas remarkable inhibition was observed on the addition of the stable 2,2,6,6-tetramethyl 4-piperidinol N-oxyl radical.The reaction mechanism was discussed.We also found that when TMPM reacted with BPO in petroleum ether,N-benzoyloxy 2,2,6,6-tetramethyl 4-piperidinyl methacrylate was formed,and this novel compound has been characterized with IR,ESR,NMR and Mass Spectroscopy.