It has been shown that the system Ni(COD)₂/BF₃? OEt₂ may polymerize norbornene with the activity of 1930 kg NB/molNi h. This catalytic system is characterized by minor content of the Lewis acid; the activity peaks at the molar ratio of B:Ni = 5. The norbornene polymerization was first demonstrated to be attended with the formation of trivalent nickel metallocyclic complexes. A monovalent nickel complex was used as a precursor for the active species.