Radical polymerizations of dialkyl itaconates were performed in benzene at 50 degreesC. The C-13 NMR spectra of the obtained polymers indicated that intramolecular chain-transfer reaction had taken place more frequently in the polymerizations of itaconates with bulkier ester groups as follows: isopropyl (i-Pr) > n-butyl (n-Bu) approximate to ethyl (Et) > methyl (Me). In addition to the C-13 NMR analysis, an electron spin resonance (ESR) analysis was conducted for polymerizations of diisopropyl itaconate, the ESR spectra of which consisted of two kinds of resonances due to the radicals with different conformations. It was assumed that the difference in conformation was attributable to the stereosequences near the propagating chain end because the relative intensity ratios of the resonances varied with the magnitude of the intramolecular chain-transfer reaction, which was accompanied by a decrease in the syndiotacticity of the obtained poly(diisopropyl itaconate)s.