Wood-polymer composites (WPC) are materials which may be prepared by impregnating wood with a variety of monomers which are subsequently polymerized by either gamma irradiation or by conventional radical initiators. The inclusion of the polymer into the wood matrix improves the physical properties of the composite compared to plain wood. The catalyst-accelerator method allows in situ polymerization of vinyl monomers at ambient conditions and thus reduces the loss of the volatile monomer during curing, which is a major disadvantage of the heat-catalyst method. The combination of peroxide initiators with an aromatic amine accelerator was optimized for the methyl methacrylate system. Polymer loadings and mechanical properties of WPC prepared from Pinus radiata using the catalyst-accelerator method were compared with those obtained using the gamma-radiation method.