The bis-[N-(substituted methyl)-salicylideneiminato]nickel/MAO systems were utilized to promote the vinylic homo-polymerization of norbornene. The results displayed that steric hindrance has significant effects on their catalytic activities for polymerization of norbomene. The complex a, bis- [N-(diphenylmethyl)-salicylideneiminato] nickel, is systematically investigated with the catalytic activity up to 4.23 x 10(8) g PNB/(mol Ni h) and the average molecular weight up to 3.26 x 10(6) g/mol. All the polymer samples obtained here are soluble at room temperature in chlorobenzene. No indication of stereoregularity was observed; this was verified by the amorphous morphology of the products. The catalytic activities, yields, molecular weights and molecular weight distributions could be controlled over a wide range via variations of the reaction parameters. (C) 2003 Elsevier B.V. All rights reserved.