Sliding wear surfaces of alumina were observed by transmission and scanning electron microscopy. Wear loss was very low (<10-7 mm3/Nm) at room temperature whereas it was high (>10-5 mm3/Nm) at 500oC. In a mild wear regime at room temperature, a layer of very fine particles (10 nm or less) is observed on the wear surface. Beneath the layer, a deformed bulk surface with extensive dislocations is observed. The layer exhibits a diffraction pattern of a meta-stable phase which is dissimilar to the original α-alumina. The layer appears to act as lubrication film at the contact interface to reduce the wear loss. In a severe wear regime at 500oC, a similar structure consisting of a fine-particle layer and deformed bulk surface is observed. However, extensive microcracks are observed in the layer and the bulk underneath that cause further material removal resulting in a high wear rate.