Nanoindentor techniques have been used to obtain the values of hardness and elastic modulus of alpha-Al2O3 polycrystalline implanted with metallic species at room temperature with 170 keV, doses ranging from 2 x 10(16) to 2 x 10(17) ions cm(-2). After implantation, annealing was performed in the temperature range 600-1400 degrees C. An attempt has been made to correlate the mechanical property modifications with physico-chemical analysis. Elastic and plastic properties of the implanted layers, of about 100 nm thickness, have been characterized by microprobe investigation. This has indicated that certain fluences and thermal annealing temperatures are favourable for the improvement of mechanical properties.