Nanocrystalline aluminum nitride powders obtained from gas condensation and in situ nitridation in a forced-flow reactor have been sintered successfully without pressure or additives. The resulting densified pellets showed good thermal conductivity and low oxygen content. A comparison of the improvement in densification with micrometer-size and nanocrystalline yttria additives was undertaken and it was found that the nanocrystalline yttria decreased the sintering temperature significantly. Besides spherical nanoparticles, needle-shaped nanocrystalline aluminum nitride particles that resulted in highly textured compacts when hot pressed could also be produced.