Both the rac- and meso-dinuclear ansa-zirconocene catalysts (mu-C12H8{[SiPh(Ind)2]ZrCl2}(2)) were prepared by a coupling reaction between 2 equiv of diindenylphenylchlorosilane (rac- and meso-isomers) and 1 equiv of p-dilithiobiphenyl in diethyl ether at -80 degrees C, followed by a successive reaction with ZrCl4 . 2THF in THF at -78 degrees C. Polymerizations of ethene and propene were conducted in a 1 dm(3) high-pressure glass reactor equipped with a mechanical stirrer at 60, 80, 100, 120, and 150 degrees C using methylalumoxane (MAO) as cocatalyst and toluene or decahydronaphthalene as the solvent. Copolymerization of ethene and 1-octene was also checked in brief. For ethene polymerization, the meso-catalyst was found to be more active, which displayed an extremely high activity to give linear polyethene with a high. molecular weight and a narrow molar mass distribution (MMD). The apparent activity increased monotonously with rising polymerization temperature from 60 degrees C up to 150 degrees C, indicating that the active species are stable even at a high temperature. On the other hand, both the rac- and meso-catalysts showed very poor activities for propene polymerization. However, copolymerization of ethene and 1-octene proceeded at a high speed.