Synthesis and radical polymerization of novel vinylcyclopropanes; 1-carboethoxy-2-trimethylsilyl-2-vinylcyclopropane (1a) and 1-carboethoxy-2-(1-trimethylsilyl)-vinylcyclopropane (1b), were examined. la and 1b were prepared by the coupling reaction of 2-trimethylsilylbutadiene with ethyl diazoacetate, which was prepared from glycine ethyl ester hydrochloride. The radical polymerization of 1a and 1b was carried out at 60 degrees C in bulk for 40 h in the presence of 2,2＇-azobis(isobutyronitrile) (5 mol % vs. monomer). Poly(1) consisted of a 1,5-ring-opened unit. Desilylation reaction of poly(1) proceeded quantitatively in aqueous hydrochloric acid.