A novel technical approach has been developed to produce highly loaded and aligned SWNT (single wall nanotubes) nanocomposites by infiltrating SWNT mats with a low viscosity resin solution. In-plane SWNT alignment is achieved by magnetically aligning the nanotubes in the buckypaper under a high magnetic field prior to the composite loading. The thermal conductivity of both magnetically aligned buckypapers and their composites have been measured. The results were analyzed with models to explain the thermal conductivity of the nanocomposites. The results show that nanotube alignment has a measurable influence on the thermal conductivities of both buckypaper and nanocomposites. The thermal conductivities were found to increase linearly with temperature for both buckypapers and composites. The thermal conductivity improvement of the nanocomposites was found to be limited. (c) 2005 Published by Elsevier B.V.