The oxidation resistance of zirconium diboride (ZrB(2)) ceramics with tungsten carbide (WC) additions was studied. ZrB(2) ceramics, nominally pure and with WC additions of 4, 5, and 6 mol%, were densified by pressureless sintering. During heating, the WC that was added to the ceramic dissolved into the ZrB(2) matrix, forming a solid solution. Oxidation behavior was evaluated using isothermal furnace oxidation at 1500 degrees C and 1600 degrees C. The presence of tungsten reduced both the weight gain and oxide scale thickness compared with nominally pure ZrB(2). After oxidation at 1600 degrees C for 3 h, the thickness of the ZrO(2) outer scale was reduced from 4.7 mm for nominally pure ZrB(2) to 0.5 mm for the ceramic containing 6 mol% WC. Analysis showed that WC additions improved the oxidation resistance of ZrB(2) by changing the morphology of the zirconia scale formed during oxidation.