A norbornene monomer carrying epoxy moiety 1 was successfully synthesized from 5-norbornene-2-carbardehyde by treating it with thioylide. With using a catalytic system consisted of palladium (II) acetate/tricyclohexylphosphine/triphenylcarbenium tetrakis(pentafluorophenyl)borate, homopolymerizations and copolymerization of 1 and 5-butyl-2-norbornene (BNB) were examined. The homopolymerization of I was slower than that of BNB presumably due to coordination of the epoxy moiety to the palladium-center in competition with the C-C double bond of norbornene. This deceleration became less significant in the copolyrnerizations with low initial feed ratios [1](0)/[BNB](0), leading to successful formation of the corresponding copolymers having a rigid poly(norbornene) main chain and epoxy moiety in the side chains, of which composition ratios agreed with the feed ratios. Influence of the epoxy moiety of 1 on its Pd-catalyzed addition polymerization was elucidated by studying the homopolymerization of BNB in the presence of 1,2-epoxyhexane. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3982-3989, 2009