Nickel (salen) in conjunction with methylaluminoxane (MAO) catalyzes the polymerization of norbornene to poly (2,3-bicyclo [2.2.1] hept-2-ene) [poly(norbornene)]. Methylaluminoxane (MAO) was used as cocatalyst as such (MAO-I) and after distilling off free trimethylaluminium (MAO-II). The catalyst system was very active in chlorobenzene at room temperature. It was also found that MAO-II gave higher activity as compared to MAO-I. The samples of polynorbornene were soluble in 1,2,4-trichlorobenzene. The poly (norbornene)s were characterized by intrinsic viscosity and thermal properties.