Addition polymerization of 5-trimethylsilyl- and endo-, exo-5,6-bis(trimethylsilyl)-norbornenes was studied in the presence of Ni-based catalytic systems: [pi-C5H9NiCl)(2)]-Et3Al2Cl3, Ni(II) naphtenate-methylaluminoxane (MAO) and (pi-C5H9NiCl)(2)-MAO. Completely saturated and soluble in aromatic solvents poly(5-trimethylsilyl-2-norbornene) was obtained with the yields up to 80%. In the course of the reaction exo-conformer was consumed much faster than endo-form independently of the type of catalytic system employed. Exo-,endo-5,6-bis(trimethylsilyl)-2-norbornene was practically inactive in the presence of the studied Ni-catalysts. At the same time its addition copolymerization with norbornene and 5-n-hexyl-2-norbornene could be readily realized. (c) 2006 Elsevier B.V. All rights reserved.