Dense 8 mol% CuO-doped 3Y-TZP ceramics were prepared by pressureless sintering for 8 h at 1500 degrees and 1550 degrees C, respectively. Transmission electron spectroscopy revealed that the ceramic sintered at 1500 degrees C exhibits grain boundaries free of any amorphous phase, while crystalline copper-oxide grains were found in the zirconia matrix, whereas the sample sintered at 1550 degrees C contains a Cu-rich amorphous grain boundary layer. The tribological behavior of these materials was tested under dry-sliding conditions using a pin-on-disk tribometer. The material sintered at 1500 degrees C showed self-lubrication resulting in a low coefficient of friction (f) of 0.2-0.3 and a low specific wear rate (k) < 10(-6) mm(3).(N.m)(-1). In contrast, the material sintered at 1550 degrees C showed poor tribological behavior (f=0.8-0.9; k > 10(-6) mm(3).(N.m)(-1) under the same conditions. The difference in the tribological behavior of these two materials was interpreted on the basis of mechanical properties and microstructural characteristics.