In this paper, a revised version of the particle growth model (PGM) describing olefin co-polymerization with metallocene catalysts is proposed. The model is used to calculate the reaction rate of hexane-propylene co-polymerization under different operating conditions. Results are compared with experimental data obtained by calorimetric technique in order to validate the model. Good agreement between calculated and experimental results is shown. (C) 2006 Elsevier Inc. All rights reserved.