Methyl acrylate is readily polymerised by the CpTiCl3-MAO system. A kinetic study shows that the reaction is characterised by a linear dependence of the rate upon methyl acrylate concentration, and by saturation behaviour with respect to both catalyst CpTiCl3 and co-catalyst MAO. The kinetic behaviour is interpreted in terms of insertion of an O-complexed monomer into a eta(3) enolate-Ti growing polymer chain. When a mixed methyl acrylate-styrene monomer system is used, a mechanism resulting in a much slower formation of a random 1: 1 co-polymer is proposed. (c) 2005 Elsevier B.V. All rights reserved.