Novel catalytic systems based on bis(chelate)nickel(II)) precursors, such as bis(alpha -nitroaceto-phenonate)nickel(II) [Ni(naph)(2)] and bis(2,6-diisopropylbenzenesalicylaldiminate)nickel(II) [Ni(dipbs)(2)], and methylaluminoxane (MAO) as the cocatalyst were employed for the polymerization of methyl methacrylate (MMA). Reaction parameters were examined. Under proper conditions, the Ni(dipbs)(2)/MAO system allowed to obtain poly(MMA) with a very high productivity (TOF lip to 70000 h(-1) and a remarkable syndiospecificity degree (rr > 80%) at room temperature without addition of an ancillary Lewis base.