Several predominantly single-phase uranium oxycarbide compositions were examined to determine the effect of oxygen content on the hot hardness, thermal diffusivity, thermal conductivity, and electrical resistivity. Little difference was noted in hot hardness over the low-temperature range; however, increased oxygen content appears to reduce the hardness above 700 deg. C. Thermal diffusivity and thermal conductivity are reduced by increased oxygen content. This decrease is most pronounced at lower temperatures, and the temperature dependence varies significantly with oxygen content. The thermal diffusivity of oxycarbides having small percentages of oxygen decreases with increasing temperature, whereas that of oxycarbides with greater oxygen content increases very slightly. The thermal conductivity data are in fair agreement with those reported for the monocarbide. Electrical resistivity is increased by increased oxygen content and shows a positive temperature dependence. The data indicate that electronic conductivity at 1,500 deg. C accounts for approximately 85 percent of the total thermal conduction at the 2-atomic percent-oxygen level and approximately 95 percent of the total at the 16-atomic percent-oxygen level.