The thermal diffusivity of particulate compounds of polymethylmethacrylate (PMMA) and aluminum powder was evaluated from measurements of temperature in samples during heating in the range of temperature between 100 and 370 K. Samples were prepared with a filler volume fraction of up to 0.15, Results were analyzed in the framework of the Hashin-Shtrikman relationship, based on variational principles, and within Nielsen's model, modified to describe thermal diffusivity. For this purpose, the dependence of specific heat and density of compounds upon temperature was calculated. It will be shown that Nielsen's model can predict the behavior of the thermal diffusivity within the whole range of temperatures of the tested compounds, while the Hashin-Shtrikman relationship underestimates the experimental values. (C) 2001 Elsevier Science Ltd. All rights reserved.