The effect of oxidation exposure on room-temperature flexural strength was examined in 3.33- and 12.51-wt%-Lu2O3-containing hot-pressed Si3N4 ceramics exposed to air at 1500degreesC for up to 1000 h. After oxidation exposure, the room-temperature strength of the ceramics was degraded, and strength retention decreased with time at temperature, dependent on the amount of additive. The retention in room-temperature strength displayed by the two compositions after 1000 h of oxidation exposure was 75%-80%. The degradation in strength was attributed to the formation of new defects at and/or near the interface between the oxide layer and the Si3N4 bulk during oxidation exposure.