The polymerization of diisopropyl itaconate (DIPI) initiated with dimethyl 2,2'-azobisisobutyrate(MAIB) was investigated kinetically in benzene. The polymerization rate (Rp) was expressed by R v = k[MAIB]°46[I)IPI] 16 at 50 °. The overall activation energy of the polymerization was calculated to be a low value of 60.2 kJ/mol. Rate constants of propagation (kp) and termination (k0 were estimated different polymerization conditions, using the ESR-determined concentrations of the propagating polymer radical. The kp value (2.4-2.9 I/mol • sec) at 50 ° shows a little increase with monomer concentration. The k t value (1.8~,.9 × 104 l/mol, sec) was fairly dependent on the chain-length of the propagating polymer radical, which is mainly responsible for the high dependence of Rp on the monomer concentration. Activation energies of initiation (E0, propagation (Ep) and termination (Et) were also determined; E i = 129.1 kJ/mol, Ep = 28.5 kJ/mol, E t = 66.1 kJ/mol. The large apparent activation energy of termination is a main origin of the low overall activation energy of the polymerization. Copolymerization of DIPI (M~) with St (M2) was also examined at 50 ° in benzene. The following copolymerization parameters were obtained according to the Kelen-Tiid6s method; r I = 0.1 I, r 2 = 0,56, Q = 0.47, e = + 0.87. Using the above results, the rate constants of cross-propagations in the copolymerization were estimated.