We investigated the thermal conductivities of AlN/GaN superlattices (SLs) by molecular dynamics simulations. We used Stillinger-Weber potentials, and we used Green-Kubo's formula to calculate thermal conductivity. It was found that thermal conductivities of SLs decrease as the SL period increases in the case of short periods, whereas thermal conductivities increase as the SL period increases in the case of long periods. We also estimated the effect of quantum dots (QDs) in AlN/GaN SLs on thermal conductivity. We found that thermal conductivities parallel to the interfaces of SLs with QDs were smaller than those without QDs. (c) 2006 Elsevier B.V. All rights reserved.