De-agglomeration of a nanocrystalline transi- tion alumina powder was performed in distilled water at its natural pH under magnetic stirring for 170 h or by ball milling for 3 h. Gibbsite appeared near transition aluminas in the magnetic stirred sample. In addition, a relevant lowering of the a-Al2O3 crystallization temperature was observed in the dispersed materials with respect to the as-received powder. However, the activation energy of the above transformation, determined by the Kissinger method, was in any case about 480-500 kJ/mol and unaffected by the dispersion route. On the contrary, it was reduced of about 10% in a-alumina seeded samples, obtained by flash plunging the powders at 1,290 C for 10 min.