As part of a program at Argonne National Laboratory (ANL) to investigate the compatibility of high-temperature sodium with materials being considered for core retention systems in liquid-metal fast breeder reactors, various commercial refractories and samples of reactor control materials were exposed to static sodium at 850°C for 5 h. The refractories tested were samples of magnesia, alumina, zirconia, mixed ceramic oxides, and graphite; the reactor control materials were boron carbide and tantalum. Samples of graphite, zirconia, and the refractories with high alumina or magnesia contents, but with low silica and chromic oxide contents, were found to be compatible with high-temperature sodium. Sample compatibility with sodium decreased with an increase in the silica content of the sample. Samples with large silica content failed completely. These results are in good agreement with results of other experiments, performed at ANL and at the Westinghouse Advanced Reactors Division, in which these materials were exposed to boiling sodium.