This article is dedicated to the study of the thermal parameters of composite materials. A nonlinear least-squares criterion is used on experimental transfer functions to identify the thermal conductivity and the diffusivity of aluminum-polymer composite materials. The density measurements were achieved to deduce the specific heat and thereafter they were compared to values given by differential scanning calorimetry measurement. The thermal parameters of the composite material polypropylene/aluminum were investigated for the two different types of aluminum filler sizes. The experimental data were compared with several theoretical thermal conductivity prediction models. It was found that both the Agari and Bruggeman models provide a good estimation for thermal conductivity. The experimental values of both thermal conductivity and diffusivity have shown a better heat transport for the composite filled with large particles. (C) 2004 Wiley Periodicals, Inc.