Superior properties of nanostructured Al2O3 based materials, such as higher hardness and fracture toughness, have been evidenced. In order to optimize their manufacturing, the mechanical activation of the starting powders (Al2O3-TiO2 and Al2O3-ZrO2) was studied. In the present work, Al2O3 powders blended with 13wt% and 44wt% of titania or 20wt% and 80wt% of yttria partially stabilized zirconia have been high-energy ball-milled using a planetary mill, P4 (Fritsch) with steel vials and balls. The effect of the milling time and operating parameters, such as shock energy and friction to total energy ratio, on the powder structural and microstructural evolutions has been determined by SEM, XRD and BET. The transformation of the metastable anatase TiO2 phase into the high pressure TiO2 II phase and rutile phase was evidenced, simultaneously to the decrease of the alumina crystallite size, in the Al2O3-TiO2 system. In the Al2O3-ZrO2 system, the transformation of the monoclinic phase and the decrease of the alumina and tetragonal zirconia crystallite size have been observed.