Sliding friction and wear tests were performed for four sintered ceramics including mullite, alumina, silicon carbide and titanium diboride (TiB 2 ), in various combinations at room temperature, 500 and 1000 o C in air. The coefficient of friction of the ceramics was nearly constant regardless of sliding combinations and test temperatures. The specific wear rates at room temperature and 500 o C were high, usually of the order of 10 - 4 mm 3 /Nm, whereas low wear rates of the order of 10 - 5 or 10 - 6 mm 3 /Nm, or even mass gain, was observed at 1000 o C. SEM observations show that tribofilms are consistently formed on the wear surfaces. A porous tribofilm, generally associated with a high wear rate at room temperature or 500 o C, is formed by compaction of debris particles. A dense tribofilm with a flat and smooth surface, often associated with a very low wear rate of the order of 10 - 6 mm 3 /Nm or less at 1000 o C, is formed by plastic deformation accompanied by dynamic recrystallization at high temperatures. A locally dense tribofilm, associated with a low wear rate of the order of 10 - 5 mm 3 /Nm at 1000 o C, is formed from the sintering of the reattached debris at high temperatures.