A joint materials test program developed by the Institute for Mining and Minerals Research (IMMR) and the Tennessee Valley Authority (TVA) involved studying the postexposure mechanical properties and corrosion behavior of candidate structural materials in an experimental, atmospheric fluidized-bed combustor (AFBC). This combustor was operated by Accurex Corporation at Research Triangle Park, North Carolina, under the direction of TVA. The materials studied were Type 304ss, Type 310ss, and INCOLOY® alloy 800 * in the form of disc coupons with and without crevice configurations. Type 304ss was also used for mechanical property measurements. The alloys were exposed to the combustor environment at ∼840 ‡C for approximately 330 hours. The ranking of alloys in terms of decreasing weight loss was found to be: (1) Type 304ss, (2) Type 310ss, and (3) INCOLOY alloy 800. The presence of tight crevices did not enhance the corrosion rate. In addition, the corrosion rates, based on the weight loss (typically 1 to 6 mpy), indicated that the alloys performed reasonably well when considering materials wastage. However, optical microscopy observations showed intergranular corrosion penetration as deep as 50 Μm in INCOLOY alloy 800 coupons and in the Type 304ss tensile specimens. The mechanical properties of the exposed Type 304ss were inferior to those of the unexposed alloy. A comparison of the data obtained from the combustor-exposed 304ss tensile samples with data from control samples exposed in vacuum to a similar thermal history indicated that the chemistry of the AFBC environment did not play a major role in the observed degradation of the mechanical properties.