The effect of alpha-Al2O3 seeding on the transformation kinetics of high purity commercial boehmite and gamma-Al2O3 was investigated. The effect of seed size, powder purity, sample homogeneity, and sample density on the transformation kinetics are discussed. The temperature and activation energy of the theta to alpha-Al2O3 phase transformation decreases for boehmite and gamma-Al2O3 powders with an appropriate addition of alpha-Al2O3 seed particles. For 5 wt.% seeded (2x10(15) seeds/cm(3) gamma-Al2O3) boehmite samples, the transformation temperature and activation energy were decreased by 85 degrees C and 115 kJ/mol, respectively, compared to unseeded boehmite. For 5 wt.% seeded gamma-Al2O3 samples, the transformation temperature and activation energy were decreased by 75 degrees C and 170 kJ/mol, respectively, compared to unseeded gamma-Al2O3.