alpha-Al2O3 powder was produced by the sol-gel process. The prepared sol-gels were seeded with 1.5 wt% powder (less than or equal to 0.12 mu m). The phase transformation of Boehmite into alpha-Al2O3 and also the particle size distribution of the transformed alpha-Al2O3 were strongly influenced by seeding and the heating rate during calcination. alpha-Al2O3 seed particles have been shown to act as a nuclei for the transition of theta- to alpha-Al2O3 and also to increase the driving force of the phase transformation, which consequently lowers the transformation temperature by about 200 degrees C. The particles derived from the seeded sol-gels retarded the formation of vermicular microstructures and were finer than those in the unseeded case. The seeding and the control of the heating rate during calcination could inhibit the grain growth due to transformation into alpha-Al2O3. Fine particles which are homogeneous and have a high sinterability at lower temperatures could be obtained.