Radical polymerizations of highly isotactic (it-) and highly syndiotactic (st-) poly(methyl methacrylate) (PMMA) macromonomers having a methacryloyl function were studied in benzene-d(6) at 60degreesC with 2,2'-azobisisobutyronitrile (AIBN). Rate of polymerization (RP) was determined from the consumption of the macromonomer by means of H-1 NMR spectroscopy. The R-p of the it-PMMA macromonomer was larger than that of the st-PMMA macromonomer. Concentrations of propagating radicals, [M-.], were estimated for the polymerization with di-t-butyl peroxide in benzene under irradiation of light at 30degreesC. The value of [M-.] for the polymerization of the st-PMMA macromonomer was larger than that for the polymerization of the it-PMMA macromonomer. The results indicated that rate constant of propagation (k(p)) for the it-PMMA macromonomer was larger than that for the st-PMMA macromonomer.