Al2O3 whiskers with an average length of 5 mu m have been synthesized from hydrothermal solution. Al(NO3)(3) and urea were mixed and put into a Teflon-lined stainless steel autoclave and then treated at 120 A degrees C to fabricate precursor whiskers NH4Al(OH)(2)CO3 (AACH). AACH whiskers were heated at 1200 A degrees C in a furnace to obtain Al2O3 whiskers. The time-dependent examinations revealed that the formation process of AACH whiskers involves two sequential processes: a short liquid-solid deposition process in the initial stage and a long Ostwald ripening process. During calcinations, AACH transforms to amorphism then to alpha-Al2O3. The escape of NH3 and CO2 induced the distortion and toothlike morphology on the surface of the Al2O3 whiskers.