The power density of 244Cm2O3 makes it an attractive fuel form for a variety of radioisotopic applications. To evaluate the compatibility of 244Cm2O3 with refractory metals for high-tem-perature applications, Ta, Ta - 10 wt% W, T-111, Mo, TZM, W, and W- 26 wt% Re were tested at 1650 and 1850°C, and Nb, Nb -1 wt% Zr, Ta, Ta- 10 wt% W, Mo, V, and Zr were tested at 1250°C for times up to 10 000 h. Serious reactions of 244Cm2O3 with Zr occurred at 1250°C and with Ta - 10 wt% W and T-111 at 1650°C. At both 1250 and 1650°C, the remaining materials showed good resistance to 244Cm2O3 with only limited attack, mainly in the form of shallow intergranular subsurface voids. At 1850°C, there was evidence of dissolution of tantalum and the tantalum alloys by 244Cm2O3. After 5000 and 10 000 h, tantalum had transferred from one portion of the capsule to another, and tantalum particles were found in the fuel. Less extensive mass transfer was noted with the other materials, although significant amounts of tungsten from the unalloyed tungsten and W - 26 wt% Re tests were found in the fuel.