A model for the homogenization of the elastoplastic properties of particle reinforced composites is proposed. The microstructure is described by means of a novel technique, consisting of generating particles in a pre-existent constrained Delaunay tetrahedralization of a cubic volume by means of a modified random adsorption algorithm. This technique allows generating models with different amounts of reinforcement by using the same finite element mesh. The obtained particle morphology is similar to that of many ceramic powders often used as reinforcement. Homogenization is carried out for a typical particle reinforced metal matrix composite with reinforcement volume fractions up to 0.25 and the representative volume element size is assessed for both elastic and elastoplastic behaviours. In this latter case the representative volume element size depends on the amount of plastic strain which develops in the matrix material and a criterion to assess the model representativeness is proposed based on the amount of elastic energy stored in the composite. The predictions of the model compare well with pertinent experimental data reported in the literature. (c) 2007 Elsevier B.V. All rights reserved.