The efficiency of a thermoelectric material is measured by the figure of merit ZT, which is inversely proportional to the thermal conductivity. Superlattice structures often have a reduced thermal conductivity because of the introduction of interface scattering and, therefore, improved performance. The present work is focused on the effective thermal conductivity of nanocomposite films. This configuration could also improve ZT because of phonon-interface scattering introduced by the nanocrystals. The effects of crystal size and mass fraction are studied numerically using a molecular dynamics simulation. Results indicate that a reduction of 25% in the effective thermal conductivity can be achieved with the addition of nanocrystals which is comparable to that found in experimental measurement. However, the effective thermal conductivity was never reduced below the alloy limit. (C) 2008 Elsevier Ltd. All rights reserved.