Syndiotactic specific polymerization of styrene has been investigated by ~(13)C NMR analysis and isotopic laelling methods. The value of the activation energy involved in the steric control has been determined. Some information of the number of the active sites and on the life of the catalysts is reported. Syndiotactic specific polymerization of styrene has been investigated by ~ (13) C NMR analysis and isotopic laelling methods. The value of the activation energy involved in the steric control has been determined. Some information of the number of the active sites and on the life of the catalysts is reported.